In the present paper, flow field in all components of a two-stage centrifugal compressor are simulated using one-dimensional method. Internal flow simulating is performed by solving basic equations of corrected empirical relations of geometry, thermodynamics and dynamics with an algorithm with iterative solution was in MATLAB. The purpose of simulation is to obtain the effect of inlet guide vanes and return channel intake angle changes on performance maps. The inputs include stagnation temperature, stagnation pressure and mass flow. The solution is done by calling the primary geometry and inlet thermodynamic and ambient conditions at the nominal speed and 70, 90 and 105 percent of the nominal speed, by applying a continuous flow with convergence of mass flow rate and Rothalpy conservation. Then in performance stability range the results of one-dimensional model are validated by empirical and three-dimensional modeling results. Then the effect of incidence angles of inlet guide vanes and return channel on compressor performance at performance maps are expressed and analyzed. This model can be used to design inlet guide vane and return channel and estimate optimized angle of guide vanes to gain maximum performance and pressure ratio.