In order to study the effect and the flow control mechanism of the dimple non-smooth surface, hemispherical dimple units were arranged in the out surface of the backdoor. The method of computational fluid dynamics(CFD) numerical simulation based on k-ω shear-stress-transport (k-ω SST) model was used to comparatively analyze the resistance characteristic, local flow field of after-body and pressure distribution of the smooth and non-smooth fuselage. According to the analysis of the local flow field and pressure distribution of the dimple, the drag reduction mechanism was obtained that the low vortex in the dimple was able to delay flow separation and the hemispherical dimple and pressure distribution of approximately constant could reduce the area of low pressure related to drag, the results of both were reducing the fuselage drag.