This paper deals with the traditional cartesian mesh to make them body-fitted based on computer graphics and local mesh refinement according to the variation of flow. Combining with the characteristics of rectangular grids and unstructured grid, the adaptive body-fitted Cartesian mesh generation program is writen and the cut-cell DSMC method is developed based on it. In order to improve the computational efficiency, some methods like local simulated molecules and dynamic time steps are used too. Numerical tests indicate that the proposed method greatly improves the search efficiency in the progress of calculation, at the same time, it also ensures body-fitted grids, high calculation accuracy and easy implementation for adaptive grids.