In the pervasive environment, intelligent taxation systems are required to be adaptive to the changing environment and the volatile requirements of taxation rules. The business rule technique is effective in achieving these kinds of adaptation. In this paper, we present an OO Petri Net based Business Rule modeling method of Intelligent Taxation System. And the structure and grammar rules of the business rule system model are proposed in detail. By using this method, we shall construct an intelligent taxation system conveniently through business rule mining. Meanwhile, the efficiency of system maintaining and modification is promoted, as well as the cost is reduced by achieving separated implementable codes and business rules. An illustrative example shows that the presented method is valid.