In the process of teaching Chinese as a foreign language,there are some structures that have different meanings with the same structure,and this causes much trouble to the foreign students when they learn and use Chinese.Transforming analysis,which is put forward by American linguist Harris,is widely used in the analysis of the Chinese grammar by Chinese linguists.This analytical method can divide ambiguous structure effectively,and reveal the semantic relations between indirect compositions so we can also use this analytical method in the access of teaching Chinese as a foreign language.By transforming,students can grasp the different meaning and usage of same structure.This thesis is going to take the usage of the function word"Gen"in the structure"N1+Gen+N2+V+(NP)" as an example,by using the analytical method of transformation,analysing the three different usages and meanings of "Gen"in this structure.