A slide rail mechanism, comprising: a first slide rail assembly comprising a first rail, a second rail and a third rail movably mounted between the first rail and the second rail, and the second rail being longitudinally movable relative to the first rail, wherein the second rail of the first slide rail assembly is arranged with a first mounting device; and a supporting assembly comprising a supporting member and a first connecting device arranged on the supporting member, wherein the first connecting device is configured to be connected to the first mounting device, characterized in that the second rail is configured to carry a carried object, and the carried object has one of a first, second and third longitudinal length; the supporting member of the supporting assembly is configured to keep the predetermined distance from the rear portion of the carried object; a second slide rail assembly, wherein the second slide rail assembly comprises a first rail, a second rail and a third rail movably mounted between the first rail and the second rail of the second slide rail assembly, the second rail of the second slide rail assembly is arranged with a second mounting device, the supporting member is further arranged with a second connecting device; wherein the first connecting device and the second connecting device are configured to be detachably connected to the first mounting device and the second mounting device respectively; the supporting member is substantially transversally arranged relative to a longitudinal direction of each of the first and second slide rail assemblies (22, 24), and the first connecting device and the second connecting device are respectively arranged adjacent to end parts of two portions (47a, 47b) of the supporting member; one of the first mounting device and the first connecting device comprises at least one engaging feature (52a, 52b, 52c), and the other one of the first mounting device and the first connecting device comprises an engaging member configured to be engaged with the at least one engaging feature (52a, 52b, 52c); the at least one engaging feature (52a, 52b, 52c) comprises a first engaging feature, a second engaging feature and a third engaging feature spaced from each other along a longitudinal direction of each of the first and second slide rail assemblies (22, 24), and the engaging member comprises an engaging part configured to be selectively engaged with one of the first engaging feature, the second engaging feature and the third engaging feature. a first slide rail assembly comprising a first rail, a second rail and a third rail movably mounted between the first rail and the second rail, and the second rail being longitudinally movable relative to the first rail, wherein the second rail of the first slide rail assembly is arranged with a first mounting device; and a supporting assembly comprising a supporting member and a first connecting device arranged on the supporting member, wherein the first connecting device is configured to be connected to the first mounting device, characterized in that the second rail is configured to carry a carried object, and the carried object has one of a first, second and third longitudinal length; the supporting member of the supporting assembly is configured to keep the predetermined distance from the rear portion of the carried object; a second slide rail assembly, wherein the second slide rail assembly comprises a first rail, a second rail and a third rail movably mounted between the first rail and the second rail of the second slide rail assembly, the second rail of the second slide rail assembly is arranged with a second mounting device, the supporting member is further arranged with a second connecting device; wherein the first connecting device and the second connecting device are configured to be detachably connected to the first mounting device and the second mounting device respectively; the supporting member is substantially transversally arranged relative to a longitudinal direction of each of the first and second slide rail assemblies (22, 24), and the first connecting device and the second connecting device are respectively arranged adjacent to end parts of two portions (47a, 47b) of the supporting member; one of the first mounting device and the first connecting device comprises at least one engaging feature (52a, 52b, 52c), and the other one of the first mounting device and the first connecting device comprises an engaging member configured to be engaged with the at least one engaging feature (52a, 52b, 52c); the at least one engaging feature (52a, 52b, 52c) comprises a first engaging feature, a second engaging feature and a third engaging feature spaced from each other along a longitudinal direction of each of the first and second slide rail assemblies (22, 24), and the engaging member comprises an engaging part configured to be selectively engaged with one of the first engaging feature, the second engaging feature and the third engaging feature.