Abstract: To improve the structural properties at the connection region of prefabricated buildings, ultra-high performance concrete (UHPC) with excellent mechanical properties is used as the permanent formwork for the connection region and a composite member is consisted by UHPC permanent formwork and the core concrete. To study the axial compressive behaviors of this new assembled UHPC-RC composite columns, the axial compressive test of short columns was carried out. The effects of steel fiber contents in precast UHPC panels and the thickness of UHPC panels on axial compressive performance, including axial compressive bearing capacity, ductility and energy absorption capacity, were investigated. The results showed that compared with normal strength concrete column, the axial compressive bearing capacity of composite column was increased by 57%~94%, and energy absorption capacity was improved by more than 100%. The axial compressive bearing capacity, ductility and energy absorption capacity of the composite column with the fiber of 3% in the UHPC jacket was 23%, 56% and 114% higher than that of the composite column with the fiber of 2%, that is, the increasing of the fiber content in the UHPC jacket from 2% to 3%, the axial behaviors of composite column can significantly improve. Based on the test results, a new model to calculate the axial bearing capacity of this new UHPC-RC composite columns was proposed, and a reduction factor of the compressive strength of UHPC was given.