Abstract: Ultra-high performance concrete (UHPC) filled square duplex stainless steel tube short column is an innovative and efficient composite structural member. In order to study the axial compressive behavior, the designed is nine UHPC-filled, three conventional concrete-filled duplex stainless steel tube short columns and, three hollow duplex stainless steel tube specimens. The main parameters include the width-to thickness ratio of duplex stainless-steel tube and the strength of core concrete. The results show that the confinement coefficient is the main factor influencing the failure mode and ultimate capacity of UHPC-filled stainless steel tube short column. With the increase of thickness of the tube from 4mm to 8mm, the failure mode of UHPC-filled duplex stainless steel tube short column specimens changed from shear type to "waist drum" type. And the average increase rate of ultimate bearing capacity of UHPC-filled square duplex stainless steel tube short column specimens is 55.43%, and the average increase rate of ductility is 17.45%. The basic mechanical properties of specimens were discussed such as strength improvement index, concrete contribution rate and, ductility index. The effect of chamfering on the stiffness of short column was analyzed. Based on the test results and confined concrete model of Mander, one prediction formula of ultimate bearing capacity of UHPC-filled square duplex stainless steel tube short column with good accuracy was established by a superposition principle.