The flow field and performance of a helicopter in common forward flight and forward flight near the ground were analyzed using CFD (computational fluid dynamics) technique. The general governing equations of turbulent flow were set up, and were directly solved by finite volume method and SIMPLER (semi-implicit method for pressure-linked equations revised) approach in Cartesian coordinates. The spinning rotor was represented as time-averaged momentum source terms distributed along the span of the rotor with functional relationship to the local flow conditions in N-S(Navier-Stokes) equations. ��K-ε�� turbulence model and wall function method were included in the calculation method. The calculated results for flow field and performance correlation show good agreement with the measured data. Therefore, the numerical simulation technique is proved to be feasible for analyzing design issues of a helicopter.