Rock-desertification is a unique environmental and ecological problem in Southwest China.As remote sensing is an important way of monitoring variation of rock-desertification

a method for measurement and information retrieval of rock-desertification is developed in this paper.MNF transform is applied to IKONOS data to reduce the number of spectral dimensions to 3.In this 3-demension

endmembers in the image are found out and analyzed.It is found that various vegetations group into a line called "vegetation line"

in which "dark vegetations"

such as coniferous forest and broadleaf forest

continuously change to "bright vegetations"

such as grasses.It is presumed that is caused by deferent proportion of shadow mixed in leaves or branches in various types of vegetation.The normalized distance between points for rock-desertification and the vegetation line is defined as Geometrical Rock-desertification Index（GRI）

which can be used to scale rock-desertification.This method was used in the IKONOS image of Puding

Guizhou province and showed many advantages.