purpose:This paper is to provide the gerneral principle and method of using the wedge filter. Materials and Methods:A concept of the irradiation angle and a equation to calculate it were introduced. The radiation angle and the given dose for each field were derived from this equation.The wedge angles of each field were got.Results: By means of the examples of laryngocarcinoma and carcinoma of maxillary sinus,the isodose graphs from the TPS using the radiation angles of the equations comfirmed this method.Conclusion: The way introduced is brief and raliable. It may help to optimize the treatment plan.