A slide rail assembly (20, 200), comprising: a first rail comprising a blocking part; a second rail movable relative to the first rail; wherein: a first lockinq device arranged on the second rail, the first locking device comprising a first member and a second member, the first member comprising a first part, the second member comprising a second part, a first space being defined between the first part and the second part, wherein the first space is not able to accommodate the blocking part; and a second locking device arranged on the second rail, the second locking device comprising a third member and a fourth member, the third member comprising a third part, the fourth member comprising a fourth part; wherein, during a process of the second rail being moved relative to the first rail from a retracted position to a first predetermined position along a first direction, the second part of the second member is configured to be blocked by the blocking part of the first rail, and the first member is configured to be moved with the second rail along the first direction, such that a second space is defined between the first part and the second part, the second space is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the first locking device; wherein the first locking device is operable to unlock the blocking part, wherein when the first locking device is operated to unlock the blocking part and the second rail is further moved relative to the first rail to a second predetermined position along the first direction, a third space defined between the third part and the fourth part is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the second locking device; characterized in that the first member is fixed to the second rail, and the second member is movable relative to the second rail within a limited range through a guiding feature. a first rail comprising a blocking part; a second rail movable relative to the first rail; wherein: a first lockinq device arranged on the second rail, the first locking device comprising a first member and a second member, the first member comprising a first part, the second member comprising a second part, a first space being defined between the first part and the second part, wherein the first space is not able to accommodate the blocking part; and a second locking device arranged on the second rail, the second locking device comprising a third member and a fourth member, the third member comprising a third part, the fourth member comprising a fourth part; wherein, during a process of the second rail being moved relative to the first rail from a retracted position to a first predetermined position along a first direction, the second part of the second member is configured to be blocked by the blocking part of the first rail, and the first member is configured to be moved with the second rail along the first direction, such that a second space is defined between the first part and the second part, the second space is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the first locking device; wherein the first locking device is operable to unlock the blocking part, wherein when the first locking device is operated to unlock the blocking part and the second rail is further moved relative to the first rail to a second predetermined position along the first direction, a third space defined between the third part and the fourth part is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the second locking device; characterized in that the first member is fixed to the second rail, and the second member is movable relative to the second rail within a limited range through a guiding feature. a first lockinq device arranged on the second rail, the first locking device comprising a first member and a second member, the first member comprising a first part, the second member comprising a second part, a first space being defined between the first part and the second part, wherein the first space is not able to accommodate the blocking part; and a second locking device arranged on the second rail, the second locking device comprising a third member and a fourth member, the third member comprising a third part, the fourth member comprising a fourth part; wherein, during a process of the second rail being moved relative to the first rail from a retracted position to a first predetermined position along a first direction, the second part of the second member is configured to be blocked by the blocking part of the first rail, and the first member is configured to be moved with the second rail along the first direction, such that a second space is defined between the first part and the second part, the second space is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the first locking device; wherein the first locking device is operable to unlock the blocking part, wherein when the first locking device is operated to unlock the blocking part and the second rail is further moved relative to the first rail to a second predetermined position along the first direction, a third space defined between the third part and the fourth part is configured to accommodate the blocking part of the first rail, in order to lock the blocking part to the second locking device; characterized in that the first member is fixed to the second rail, and the second member is movable relative to the second rail within a limited range through a guiding feature.