Abstract: Digital terrain model (DTM) is an important component of a resource information system. The DTM with netted texture has the advantage of fixed position and altitude. It has many uses. This paper described in detail the principle and method of altitude data extraction, slope and aspect data calculation, change of net density, establishment of terrain model and three dimension map-making. The function of the DTM subsystem under microcomputer environment was also introduced. The DTM established within this subsystem can be used in image processing of remote sensing, classification of vegatation, stratification of site condition, map-making of slope and aspect. It can also be used in selecting road, quantity calculation of earthwork, selecting location of reservoir, calculation of dam height and capacity of reservoir, disaster estimation of floodwater and so on.