Circular steel tube filled with rigid polyurethane foam (RPUF) with density of 300 kg/m³ was proposed for energy absorbing components according to the requirement of civil engineering. Three groups of empty steel tubes and three groups of RPUF-filled short circular steel tubes were tested under axial compressive load to gain their mechanical properties and ability of energy absorbing. Experimental results show that filling RPUF could effectively transform the plastic bucking behavior of circular steel tube under axial compressive load from asymmetric mode towards symmetric mode. The first peak load and structural crashworthiness indicators of the RPUF-filled steel tube increased significantly. The thinner the wall thickness was, the greater the increased. Moreover, a finite element model of RPUF-filled short circular steel tube was built based on the ABAQUS/Explicit, and simulation results showed good agreement with experimental results, which confirmed the accuracy of the model. Parameters analysis was carried out subsequently, which showed that the energy absorbing ability of the RPUF-filled circular steel tube increased with its wall thickness and tube diameter increase. An effective prediction formula for mean crush load (MCL) was also deduced based on the classical progressive collapse model proposed by Alexander. After comparison with the experimental and simulation results, it is found that this formula can effectively predict the average compressive force of the RPUF-filled short circular steel tube.