In the case of small increase of cross-section, concrete column strengthened by circular steel tube can increase the bearing capacity greatly as well as ductility. This has resulted in engineering welcome. This paper studied the common work performance of reinforced concrete column strengthened by circular steel tube in three different conditions test of axial compression. The results show that outsourcing steel and core column can be achieved interaction. By strengthening, it can improve the load capacity of the concrete column as well as ductility. With the increase in initial load, although it has little effect on the bearing capacity of reinforced columns, it can affect the ductility to some extent. This paper can provide experimental basis for engineering applications.