A system comprising a chassis (10, 402), a rack (14, 410) and a slide rail assembly (12, 404), adapted to mount the chassis (10, 402) to the rack (14, 410), the slide rail assembly (12, 404) comprising: a first rail; a second rail (40, 202, 302) longitudinally displaceable relative to the first rail, the second rail (40, 202, 302) being mountable to the chassis (10, 402); and a bracket (16, 406) to mount the slide rail assembly (12, 404) to the rack (14, 410), the bracket (16, 406) comprising a side plate connected to the first rail, an end plate bent from the side plate, and a movable member (30, 408) movably connected to the side plate, wherein the movable member (30, 408) has at least one retaining portion (34, 412) and is movable to an opened position and a closed position, in which in the assembled state the retaining portion of the movable member is blocked by a first post of the rack (14, 410) to ensure that the bracket (16, 406) will not fall off from said first post, and wherein the retaining portion (34, 412) corresponds to the end plate when the movable member (30, 408) has been operated and thereby moved to the closed position; wherein the second rail (40, 202, 302) or the chassis (10, 402) having a retaining member (42, 200, 300, 400), and wherein when the second rail (40, 202, 302) has been retracted relative to the first rail, the retaining member (42, 200, 300, 400) is able to restrict movement of the movable member (30, 408) from the closed position to the opened position, wherein the retaining member (42, 200, 300) is connected to the second rail (40, 202, 302) by a connecting means or the retaining member is connected to the chassis by an attaching means or the retaining member is connected to the chassis by being integrally formed with the chassis. a first rail; a second rail (40, 202, 302) longitudinally displaceable relative to the first rail, the second rail (40, 202, 302) being mountable to the chassis (10, 402); and a bracket (16, 406) to mount the slide rail assembly (12, 404) to the rack (14, 410), the bracket (16, 406) comprising a side plate connected to the first rail, an end plate bent from the side plate, and a movable member (30, 408) movably connected to the side plate, wherein the movable member (30, 408) has at least one retaining portion (34, 412) and is movable to an opened position and a closed position, in which in the assembled state the retaining portion of the movable member is blocked by a first post of the rack (14, 410) to ensure that the bracket (16, 406) will not fall off from said first post, and wherein the retaining portion (34, 412) corresponds to the end plate when the movable member (30, 408) has been operated and thereby moved to the closed position; wherein the second rail (40, 202, 302) or the chassis (10, 402) having a retaining member (42, 200, 300, 400), and wherein when the second rail (40, 202, 302) has been retracted relative to the first rail, the retaining member (42, 200, 300, 400) is able to restrict movement of the movable member (30, 408) from the closed position to the opened position, wherein the retaining member (42, 200, 300) is connected to the second rail (40, 202, 302) by a connecting means or the retaining member is connected to the chassis by an attaching means or the retaining member is connected to the chassis by being integrally formed with the chassis.