In order to correctly analyze the control dependence and data dependence relations of C program,and then carry out the program slicing,code redundancy and code duplication detection,a method to extract the static information of C program from GCC AST text was put forward.Firstly,the GCC AST text was standardized and the nodes unrelated to control dependence and data dependence analysis were eliminated.Secondly,control dependence subgraph was constructed.If data flow analysis was necessary,control flow graph was constructed based on control dependence subgraph and data dependence subgraph was constructed based on control flow graph.At last,by the introduction of inter-process analysis,system dependence graph was improved.It is indicated that the research can correctly analyze the control dependence and data dependence relations.