The invention provides a method for efficiently converting a TIN model into a Grid model under a DEM architecture. According to the adopted conversion method, conversion is completed only by traversing the irregular triangle table. A complex data structure in the process of constructing the irregular triangulation network is avoided. Therefore, the method disclosed by the invention is relatively simple to implement. Computing speed is also comparatively fast, the range is determined according to the irregular triangle. Therefore, the search range of the corresponding grid points becomes very small. Meanwhile, the coordinate reduction processing in the calculation process is also beneficial to improving the efficiency, and conversion experiments are carried out on grids with different densities. Obtained results show, compared with a method in the prior art, the conversion time of different grid intervals and the conversion time of different resolutions are obviously shortened. The timeis saved by 26% or above, and the method is small in resource occupation, small in error before and after conversion, free of frequent maintenance, small in error probability, capable of being well popularized to practical application and high in practical value.