For fan-cooled motors, the fan performance directly influences the thermal performance of the motor and so its lifetime. A 10-degree temperature reduction could extend the motor electrical insulation lifetime twofold. The purpose of this study is to apply computational fluid dynamics (CFD) modeling techniques to a motor fan system and use the validated CFD model to analyze key design parameters. Simulation results and measured data at various fan speeds showed good agreement between CFD results and the test data. In addition, both the calculated and measured flow rates and torques follow fan laws very well. The validated CFD model is used to perform a parametric study for the fan system. The effect of axial clearance between the fan and the fan cover and between the fan and the bracket, the effect of the fan cover diameter, and the effect of the number of fan blades and their chord length, on fan performance are studied. We demonstrated the capability of applying CFD to complicated geometry to effectively analyze the design parameters.