Evaluating status and possibility of desertification is an important field in arid and semi-arid zone. For Gansu province is located in inner northwestern China, fragile environment and irrational human activity have made it a relatively serious area of desertification in northern China, and a main source of dust storm happening in China every year as well as. The paper acquires data of variety of land use and desertification on Gansu province from 1986 to 2000, by interpreting TM images of the two periods with GIS software ARC/INFO. Then, on the basis of the data, the study uses index of desertification extent to analyze spatial pattern of desertification on the province. The result indicates that on desertification scale, the Hexi corridor exceeds the other areas, in contrast to it that desertification extent of the Hexi corridor is less than it of the other areas. Based on the above results, with support of integration of ARC/INFO, statistic software SPSS and office software EXCEL, the study uses means of principal component analysis (PCA) to evaluate potential extent of every county on possibility of desertification. The result shows that the possibility of desertification of the Hexi corridor and the Gannan region exceed it of other areas, which is in accord with present spatial pattern of desertification scale on Gansu province.