Abstract: The resolution of digital elevation models is a basic parameter to generate DEM.However,those studies about how to decide the resolution of DEM didn't take the points number into account.We analyze RMSE of Elevation of ANUDEM and TIN-DEM,which are generated by the data extracted from aero photos by digital photogrammetric method.The results show that the point density for building ANUDEM with 2 m RMSE of elevation and 5 m grid size should be more than 7 000 points/km2,while for TINDEM,it should be more than 8 500 points/km2 at 1∶100 00 scale level.Moreover,RMSE of elevation keeps stable when the grid size is finer than 20 m and the point density is in the range between 7 400 and 9 400 points/km2.