A slide rail assembly comprising: a first rail comprising a first end, a second end, and a passage positioned between the first end and the second end of the first rail, the passage of the first rail comprising a passage opening; a second rail comprising a first wall, a second wall, and a longitudinal wall connected between the first wall and the second wall of the second rail; a third rail, the first rail being movably mounted between the third rail and the second rail; and an auxiliary member arranged adjacent to the passage opening of the first rail, the auxiliary member comprising an arced contour; characterized in that the slide rail assembly further comprises: a reinforcement member connected to the third rail and exceeding a first end portion of the third rail, the reinforcement member comprising: a first portion; a second portion; and a longitudinal portion connected between the first portion and the second portion of the reinforcement member; a first bracket device configured on the reinforcement member, and the first bracket device being configured for providing a first post for the third rail to be mounted on a rack; a supporting member arranged on the first rail, the supporting member comprising an arced contour, and when the first rail is moved relative to the third rail, the first rail being in contact with the reinforcement member via the arced contour of the supporting member; and a connecting member connected to an extension section of the first rail exceeding the first end of the first rail for a predetermined distance, the connecting member comprising a holding structure located at a position corresponding to one of the first portion and the second portion of the reinforcement member; wherein the auxiliary member and the supporting member are pivotally connected to the connecting member through a first shaft and a second shaft respectively and positioned at different positions; wherein the second rail is inserted in the passage of the first rail from the passage opening of the first rail through being guided by the arced contour of the auxiliary member; wherein the holding structure is configured to hold the first portion of the reinforcement member and comprises a first wall section, a second wall section, and a third wall section that are bent relative to one another, the third wall section is positioned between the first wall section and the second wall section, the first wall section, the second wall section, and the third wall section jointly define a space, and the first portion of the reinforcement member passes through the space. a first rail comprising a first end, a second end, and a passage positioned between the first end and the second end of the first rail, the passage of the first rail comprising a passage opening; a second rail comprising a first wall, a second wall, and a longitudinal wall connected between the first wall and the second wall of the second rail; a third rail, the first rail being movably mounted between the third rail and the second rail; and an auxiliary member arranged adjacent to the passage opening of the first rail, the auxiliary member comprising an arced contour; characterized in that the slide rail assembly further comprises: a reinforcement member connected to the third rail and exceeding a first end portion of the third rail, the reinforcement member comprising: a first portion; a second portion; and a longitudinal portion connected between the first portion and the second portion of the reinforcement member; a first portion; a second portion; and a longitudinal portion connected between the first portion and the second portion of the reinforcement member; a first bracket device configured on the reinforcement member, and the first bracket device being configured for providing a first post for the third rail to be mounted on a rack; a supporting member arranged on the first rail, the supporting member comprising an arced contour, and when the first rail is moved relative to the third rail, the first rail being in contact with the reinforcement member via the arced contour of the supporting member; and a connecting member connected to an extension section of the first rail exceeding the first end of the first rail for a predetermined distance, the connecting member comprising a holding structure located at a position corresponding to one of the first portion and the second portion of the reinforcement member; wherein the auxiliary member and the supporting member are pivotally connected to the connecting member through a first shaft and a second shaft respectively and positioned at different positions; wherein the second rail is inserted in the passage of the first rail from the passage opening of the first rail through being guided by the arced contour of the auxiliary member; wherein the holding structure is configured to hold the first portion of the reinforcement member and comprises a first wall section, a second wall section, and a third wall section that are bent relative to one another, the third wall section is positioned between the first wall section and the second wall section, the first wall section, the second wall section, and the third wall section jointly define a space, and the first portion of the reinforcement member passes through the space.