A slide rail assembly for mounting a chassis to a rack is provided. The chassis has multiple mounting members on a lateral side. The slide rail assembly is mounted on the rack by two brackets and includes first and second rails, a first auxiliary supporting member, and multiple reinforcing segments. The first rail has first and second sides, wherein the first side has a concave space. The second rail can be displaced with respect to the first rail and has an inner side and an outer side. The first auxiliary supporting member is mounted in the concave space of the first side of the first rail. The reinforcing segments are fixedly mounted on the inner side of the second rail.