Abstract: The Instability of compression members of space structures is one of the important causes of structural failure. The sleeves were applied to reinforce the compression members in space structures to restrain the buckling of the compression members, and to improve the ultimate bearing capacity and the ductility of the components. Thusly, axial compression tests were conducted on 12 specimens to investigate the ultimate bearing capacity, the failure modes and, the ductility of the compression members with and without sleeves. Key parameters include the sleeves thickness, the gap between the inner compression members and sleeves, and the overhang length of the inner compression members. The maximum increment for the ultimate bearing capacity of the specimens after reinforcing was 146%. Besides, the bearing capacity increased with the increase of the sleeves thickness and, with the decrease of the overhang length of the inner compression members. The bearing capacity decreased slightly with the gap between the inner compression members and the sleeves. After reinforcing the compression members, the failure modes of the components changed from the overall instability of the compression members to the coupling instability of compression members and their inner overhangs. Moreover, the overall instability was prone to occur with the decrease of the sleeves thickness. The instability of the overhang of the inner compression members was likely to be observed with the overhang length. The influence of gap on the failure modes was not obvious. In addition, the ductility of all specimens with sleeves is larger than that of the specimens without sleeves, and the ductility index could be more than doubled with reasonable design.