Parameters identification and determination are important in the fuel cell model development, especially for multiphysic modeling which includes many sensitive semiempirical parameters. In this paper, the parameter sensitivities are investigated based on a well-developed 1.2-kW multiphysic proton exchange membrane fuel cell model. Moreover, to get a complete fuel cell system model, the models of auxiliaries such as the air compressor and cooling fan are developed. Through the analysis, the effect of some physical parameters on the fuel cell performance are obtained. Specifically, stack temperature is a crucial parameter which influences not only the output voltage, but also the water content in the fuel cell membrane. The influence of nonuniform distribution of temperature on the fuel cell model is discussed as well, including the end plate and local heating effects.