Pamir, in Tajikistan, located in alpine region, relatively lower geological researching level, lacks complete topographies with the scale of 1 to 50 000 and 1 to 100 000. According to the above matter, the project carries on monographic studies. Based on the ASTER-GDEM elevation data, platform of ARCGIS 9.0, disposing DEM data, the authors successfully extracted the topography and water system with the accuracy of 25 m. At the same time, the comparison between the extracted data and actual data indicates that the topographic data extracted is reliable and credible, and the accuracy is close to the scale of 1 to 50 000. And finally the problem encountered above was solved, a new, quick and effective method for abroad geological survey is provided.