Experiments on axial compression behaviors of 13 steel-polyurethane composite tube(SPCT)specimens were conducted to study the application of polyurethane to steel composite tubes. The results show that, under the axial compression, the SPCT was shaped like a bow drum. When local buckling occurred in the steel tube, polyurethane could effectively delay the buckling and deformation. Over the whole loading process, the bonding performance between polyurethane and steel was so good that peeling did not occur. It can be seen from the load-displacement curve and test process that the load-displacement curve is generally composed of elastic, elastic-plastic, descending, and strengthening phases, indicating that the SPCT has sound ductility and a reserve of strength to resist dynamic loads such as earthquakes. With the decrease of L/D, the limiting load of the specimen had an increasing trend, but the trend was not significant. The confining parameter ξ is an important factor influencing the specimen. When ξ increased, the specimen’s carrying capacity increased significantly, and vice versa.