This paper describes the application of finite difference algorithms in MT method, deduces the algorithms of 1D layered and continuous medium, and proposes a new mesh generation method. Meanwhile, with two-layer or three-layer medium model inversion calculation, the paper demonstrates the correctness of the algorithms and rationality of the grid subdivision method. The authors also designed a kind of continuous medium and made a comparison of the inversion result between two kinds of multiple layered medium models which have different layer approximations, and indicated the necessity of continuous medium model inversion research. For continuous medium model, the fine the grid, the better the approach result. Nevertheless, with the gradual decreasing of the error, the improvement of accuracy becomes not so distinct. However, resource and time consumption will dramatically increase. So decreasing grid spacing without restriction is not necessary. What's more, taking both the error and grid spacing into consideration, the authors conducted second difference calculation in first mesh generation and achieved a new conclusion, which can distinctly improve the calculation result.