According to the theory of the multi-grid scheme, this paper puts forward a new multiple-grid scheme in the calculation of the diffuser grid flow field of NASA67, which is used with the combination of explicit time marching method, finite volume difference code and distributed body force. By using Navier-Stokes equations, Baldwin-Lomax algebraic turbulence model, finite volume method and Runge-Kutta time stepping schemes it analyzes the flow field of diffuser grid. The use of the multi-grid scheme makes the converging speed evidently increase. The calculation result tallies with the experimental result.