A novel approach to modelin8 resonant conventers, was presented in this paper.The variant subtopologies of a converfer are unified into an equiualent topology by the periodicpulse functions;Laplace transforms of the sampled function ,insteady of continuous ,of a small sig-nal variable are made;furthermore,the linear approximation is processed according to the differenttypes of converters, The conventional series and parallel converters are used as examples to discussthe principles of the approach. Finally the computer calcultion data is compared with the experiment results to con firm the models to be correct.