A slide rail assembly configured to be applied to a rack, the slide rail assembly comprising: a first bracket device comprising a supporting frame, a bracket and a fastening member, the bracket being arranged on the supporting frame, the fastening member being configured to fasten a first post of the rack through a fastening portion thereof, such that the slide rail assembly is mounted on the first post through the first bracket device; a driving device, wherein the driving device and the first bracket device are longitudinally movable relative to each other; and a rail member, wherein the rail member and the first bracket device are longitudinally movable relative to each other; characterized in that the rail member is moved relative to the first bracket device from a first predetermined position along a first direction by a predetermined traveling distance, the rail member is able to drive the driving device to move from a first position to a second position, in order to drive the fastening member of the first bracket device to switch from a first state into a second state; wherein the driving device comprises a first driving feature, the rail member comprises a first structure, the rail member is able to abut the first driving feature through the first structure to drive the driving device move along the first direction from the first position to the second position; the driving device further comprises a second driving feature, the rail member further comprises a second structure, the rail member is able to abut the second driving feature through the second structure to drive the driving device move along a second direction opposite to the first direction from the second position to the first position, in order to drive the fastening member of the first bracket device to switch from the second state into the first state. a first bracket device comprising a supporting frame, a bracket and a fastening member, the bracket being arranged on the supporting frame, the fastening member being configured to fasten a first post of the rack through a fastening portion thereof, such that the slide rail assembly is mounted on the first post through the first bracket device; a driving device, wherein the driving device and the first bracket device are longitudinally movable relative to each other; and a rail member, wherein the rail member and the first bracket device are longitudinally movable relative to each other; characterized in that the rail member is moved relative to the first bracket device from a first predetermined position along a first direction by a predetermined traveling distance, the rail member is able to drive the driving device to move from a first position to a second position, in order to drive the fastening member of the first bracket device to switch from a first state into a second state; wherein the driving device comprises a first driving feature, the rail member comprises a first structure, the rail member is able to abut the first driving feature through the first structure to drive the driving device move along the first direction from the first position to the second position; the driving device further comprises a second driving feature, the rail member further comprises a second structure, the rail member is able to abut the second driving feature through the second structure to drive the driving device move along a second direction opposite to the first direction from the second position to the first position, in order to drive the fastening member of the first bracket device to switch from the second state into the first state.