By using a group of correlation equations of the major components, a large algebra equations system has been established to simulate general performance of an automotive AC system on a trial vehicle. Newton-Raphson numerical method is employed to conduct the solving of the non-linear equation system. Specific solutions have been found on a combination of the condenser's fin density, compressor type, and evaporator air quantity. The simulation result has demonstrated decent rationality on the primary systematic parameters such as the cab temperature, the system pressure profile, as well as the system COP etc. Mathematically, the simulation showed up desirable convergence and fast speed in the equation solving.