A slide rail assembly, comprising: a first rail having a first end, the first rail having a first side and a second side opposite to the first side, the first rail comprising a first wall, a second wall and a longitudinal wall connected between the first wall and the second wall of the first rail, and the first wall and the second wall of the first rail being located at the first side; a second rail longitudinally movable relative to the first rail at the first side of the first rail, the second rail having a first end; an extension member arranged at the second side of the first rail, and the extension member being extended beyond the first end of the first rail; a first bracket arranged on the extension member, the first bracket comprising a side wall and at least one first mounting member located adjacent to the side wall; and a second bracket, wherein at least one of the first bracket and the second bracket is longitudinally movable relative to the first rail; wherein the second bracket comprises a side part and at least one second mounting member located adjacent to the side part, the side part is arranged with a supporting member; characterized by: a supporting feature arranged on the first bracket; wherein when the second rail is located at a retracted position relative to the first rail, the first end of the second rail is not extended beyond the supporting feature; wherein the supporting member has at least one first supporting section and at least one second supporting section connected to the at least one first supporting section, the at least one first supporting section is configured to support one of the first wall and the second wall of the first rail, and the at least one second supporting section is configured to support one of a first predetermined part and a second predetermined part of the extension member; wherein the at least one first supporting section and the at least one second supporting section of the supporting member are located on different longitudinal planes, and a longitudinal length of the at least one second supporting section is greater than a longitudinal length of the at least one first supporting section. a first rail having a first end, the first rail having a first side and a second side opposite to the first side, the first rail comprising a first wall, a second wall and a longitudinal wall connected between the first wall and the second wall of the first rail, and the first wall and the second wall of the first rail being located at the first side; a second rail longitudinally movable relative to the first rail at the first side of the first rail, the second rail having a first end; an extension member arranged at the second side of the first rail, and the extension member being extended beyond the first end of the first rail; a first bracket arranged on the extension member, the first bracket comprising a side wall and at least one first mounting member located adjacent to the side wall; and a second bracket, wherein at least one of the first bracket and the second bracket is longitudinally movable relative to the first rail; wherein the second bracket comprises a side part and at least one second mounting member located adjacent to the side part, the side part is arranged with a supporting member; characterized by: a supporting feature arranged on the first bracket; wherein when the second rail is located at a retracted position relative to the first rail, the first end of the second rail is not extended beyond the supporting feature; wherein the supporting member has at least one first supporting section and at least one second supporting section connected to the at least one first supporting section, the at least one first supporting section is configured to support one of the first wall and the second wall of the first rail, and the at least one second supporting section is configured to support one of a first predetermined part and a second predetermined part of the extension member; wherein the at least one first supporting section and the at least one second supporting section of the supporting member are located on different longitudinal planes, and a longitudinal length of the at least one second supporting section is greater than a longitudinal length of the at least one first supporting section. a supporting feature arranged on the first bracket; wherein when the second rail is located at a retracted position relative to the first rail, the first end of the second rail is not extended beyond the supporting feature; wherein the supporting member has at least one first supporting section and at least one second supporting section connected to the at least one first supporting section, the at least one first supporting section is configured to support one of the first wall and the second wall of the first rail, and the at least one second supporting section is configured to support one of a first predetermined part and a second predetermined part of the extension member; wherein the at least one first supporting section and the at least one second supporting section of the supporting member are located on different longitudinal planes, and a longitudinal length of the at least one second supporting section is greater than a longitudinal length of the at least one first supporting section.