A slide rail assembly comprising: a first rail having a first end and a second end opposite to the first end , the first rail comprising an upper wall , a lower wall and a side wall connected between the upper wall and the lower wall , a passage being defined by the upper wall , the lower wall and the side wall of the first rail ; a second rail accommodated in the passage of the first rail and movable relative to the first rail , the second rail comprising an upper wall corresponding to the upper wall of the first rail , the upper wall of the second rail having a recessed part ; and at least one supporting member movably mounted between the upper wall of the first rail and the upper wall of the second rail , a portion of the at least one supporting member being accommodated in the recessed part , the at least one supporting member configured to support the second rail ; wherein when the at least one supporting member is moved from a first position to a second position, the portion of the at least one supporting member is extended beyond the first end of the first rail characterized by that the second rail has a first driving part and a second driving part , the second rail is configured to drive the at least one supporting member through the first driving part along a first direction to move the at least one supporting member from the first position (P1) to the second position (P2), the second rail is configured to drive the at least one supporting member through the second driving part along a second direction to move the at least one supporting member from the second position to the first position. a first rail having a first end and a second end opposite to the first end , the first rail comprising an upper wall , a lower wall and a side wall connected between the upper wall and the lower wall , a passage being defined by the upper wall , the lower wall and the side wall of the first rail ; a second rail accommodated in the passage of the first rail and movable relative to the first rail , the second rail comprising an upper wall corresponding to the upper wall of the first rail , the upper wall of the second rail having a recessed part ; and at least one supporting member movably mounted between the upper wall of the first rail and the upper wall of the second rail , a portion of the at least one supporting member being accommodated in the recessed part , the at least one supporting member configured to support the second rail ; wherein when the at least one supporting member is moved from a first position to a second position, the portion of the at least one supporting member is extended beyond the first end of the first rail characterized by that the second rail has a first driving part and a second driving part , the second rail is configured to drive the at least one supporting member through the first driving part along a first direction to move the at least one supporting member from the first position (P1) to the second position (P2), the second rail is configured to drive the at least one supporting member through the second driving part along a second direction to move the at least one supporting member from the second position to the first position. <EOS>