This work is focused on the reduction of the aerodynamic resistance of a microbus. The approach is the three dimensional (3-D) numerical simulation. The RNG k–ε turbulence models are adopted in the computation. Based on the model of SC6350 Chang’an microbus and the improved rear shape, the aerodynamic characteristics of both models at different speeds are studied. Flow maps drawn on the basis of the computed results can offer a reliable method to study the flow field around a microbus. The computed results can give a reference for study of the aerodynamic resistance reduction on a microbus for energy saving. And the results of the optimized shape can provide a theoretical basis for the related research.