A slide rail assembly (20, 200), comprising: a first rail; a second rail movable relative to the first rail; a blocking member arranged on one of the first rail and the second rail; a working member arranged on the other one of the first rail and the second rail; and an operating member (36, 202) operatively movable between a first predetermined position and a second predetermined position; wherein when the second rail is moved relative to the first rail from a retracted position to an extension position along an opening direction, the working member and the blocking member are configured to block each other in order to prevent the second rail from being moved from the extension position toward the retracted position along a retracting direction; wherein when the operating member (36, 202) is operated to move from the first predetermined position to the second predetermined position, the operating member (36, 202) is configured to contact one of the working member and the blocking member, in order to keep the working member and the blocking member in a state without blocking each other; characterized in that when the user stops applying the force to the operating member, the operating member is not forced to move from the second predetermined position to the first predetermined position; wherein when the operating member is operated to move from the first predetermined position to the second predetermined position, the operating member is configured to stay at the second predetermined position and keep one of the working member and the blocking member in a non-blocking state through a driving part to prevent the working member and the blocking member from blocking each other, so as to allow the second rail to be retracted from the extension position along the retracting direction; wherein the operating member is configured to be operated manually by the user to return to the first predetermined position from the second predetermined position. a first rail; a second rail movable relative to the first rail; a blocking member arranged on one of the first rail and the second rail; a working member arranged on the other one of the first rail and the second rail; and an operating member (36, 202) operatively movable between a first predetermined position and a second predetermined position; wherein when the second rail is moved relative to the first rail from a retracted position to an extension position along an opening direction, the working member and the blocking member are configured to block each other in order to prevent the second rail from being moved from the extension position toward the retracted position along a retracting direction; wherein when the operating member (36, 202) is operated to move from the first predetermined position to the second predetermined position, the operating member (36, 202) is configured to contact one of the working member and the blocking member, in order to keep the working member and the blocking member in a state without blocking each other; characterized in that when the user stops applying the force to the operating member, the operating member is not forced to move from the second predetermined position to the first predetermined position; wherein when the operating member is operated to move from the first predetermined position to the second predetermined position, the operating member is configured to stay at the second predetermined position and keep one of the working member and the blocking member in a non-blocking state through a driving part to prevent the working member and the blocking member from blocking each other, so as to allow the second rail to be retracted from the extension position along the retracting direction; wherein the operating member is configured to be operated manually by the user to return to the first predetermined position from the second predetermined position.