Finding simple, non recursive, base noun phrase is an important step for many natural language processing applications. This paper presents a new corpus based approach using decision tree for that purpose. In contrast to previous methods for Base NP identification, we adopt a decision tree trained from Penn Treebank to identify Base NP. And a self learning mechanism is further integrated into our model. Experimental results show good performances using our method. The method can also be applied to processing of any other language.