To quantitatively analyze the effect of debonding between steel tube and filled concrete on the ultimate bearing capacity of CFST arch bridge,a calculation model was proposed based on reasonable assumptions.The calculation program was written by using finite element method,and used to simulate the process of debonding between steel tube and filled concrete.The program was verified.By taking a single tube CFST arch bridge as a case study,the calculation results show that under uniformly distributed load on full span,the complete debonding makes the ultimate bearing capacity of single tube CFST arch bridge decreased about 10%.