Abstract: A core and bypass combined calculation method of full-speed performance and surge boundary of the multi-stage double-channel fan/compressor was established.The circumferentially averaged Euler equations with two modeling source terms were employed to reduce the overall computation effort,while modeling blade force and friction force were employed along with incidence angle and deviation angle proposed by NASA SP-36 to model the two source terms.By combining with Koch surge boundary model,the simulation program was conducted for the overall aerodynamic performance of one transonic fan stage and a high bypass ratio fan/compressor.As compared with experiment and 3-D simulation,the results show the circumferentially averaged method can fulfill the requirement of practical application.