The high level synthesis approach based on PSA is proposed.The datapath represented by PSA was constructed with the library elements firstly,then the basis of polynomial representation datapath was computed.Some operations were implemented using basis,such as multivariate polynomial decomposition,the grea test common divisor extraction,library mapping and so on,thus the optimization of datapath with these operations was achieved.The complexity analysis of algorithm was carried out.The experiment was implemented on the SUN station with Maple10.The results show the efficiency our method.