Abstract: An expert system developed for the explanation of induced polarization anomaly is presented in detail.In this system,the domain expert knowledge is jointly represented with produc- tion rules and procedure method.The system employs a hybrid reasoning engine to simulate the prob- lem solving process of human expert.Semi-automatic knowledge acquisition tool and consistence check to some extent are tailored for the construction of level structured knowledge base.Moreover,the system also provides users with the stricted natural language explanation effect by tracing the reference path.