A slide rail assembly, comprising: a first rail arranged with a first blocking feature; a second rail arranged with a second blocking feature comprising a main body part, at least one extension leg and an abutting part and being movable relative to the first rail; and a third rail movable relative to the second rail; wherein the second rail is movably mounted between the first rail and the third rail; wherein when the second rail is moved relative to the first rail along a first direction to a first open position, the second blocking feature is blocked by the first blocking feature in order to prevent the second rail from being moved from the first open position along the first direction; wherein one of the first blocking feature and the second blocking feature is configured to be operated to move away from each other with the second blocking feature being no longer blocked by the first blocking feature, in order to allow the second rail to be moved from the first open position along the first direction to be further detached from the first rail; the slide rail assembly characterized by: an operating member configured to be operated to drive the second blocking feature to move, wherein the second rail further comprises a through hole facing the first rail, and the second blocking feature passes through the through hole; wherein the operating member is an elastic piece and has a connecting part fixed to the side wall of the second rail and an elastic part connected to the connecting part of the operating member, the elastic part has a mounting hole for allowing the at least one extension leg of the second blocking feature to extend therein, the elastic part of the operating member is configured to support the at least one extension leg of the second blocking feature. a first rail arranged with a first blocking feature; a second rail arranged with a second blocking feature comprising a main body part, at least one extension leg and an abutting part and being movable relative to the first rail; and a third rail movable relative to the second rail; wherein the second rail is movably mounted between the first rail and the third rail; wherein when the second rail is moved relative to the first rail along a first direction to a first open position, the second blocking feature is blocked by the first blocking feature in order to prevent the second rail from being moved from the first open position along the first direction; wherein one of the first blocking feature and the second blocking feature is configured to be operated to move away from each other with the second blocking feature being no longer blocked by the first blocking feature, in order to allow the second rail to be moved from the first open position along the first direction to be further detached from the first rail; the slide rail assembly characterized by: an operating member configured to be operated to drive the second blocking feature to move, wherein the second rail further comprises a through hole facing the first rail, and the second blocking feature passes through the through hole; wherein the operating member is an elastic piece and has a connecting part fixed to the side wall of the second rail and an elastic part connected to the connecting part of the operating member, the elastic part has a mounting hole for allowing the at least one extension leg of the second blocking feature to extend therein, the elastic part of the operating member is configured to support the at least one extension leg of the second blocking feature. an operating member configured to be operated to drive the second blocking feature to move, wherein the second rail further comprises a through hole facing the first rail, and the second blocking feature passes through the through hole; wherein the operating member is an elastic piece and has a connecting part fixed to the side wall of the second rail and an elastic part connected to the connecting part of the operating member, the elastic part has a mounting hole for allowing the at least one extension leg of the second blocking feature to extend therein, the elastic part of the operating member is configured to support the at least one extension leg of the second blocking feature.