In this paper, a new SAW filter design tool based on RF circuit design software has been developed. Using this new design tool, the design methods of S band SAW filter has been investigated. In order to analysize the packaging on the performances of SAW filter under high frequency, the lumped parameter model of packaging has been established. A SAW filter at 2.2 GHz,with the insertion loss of -3 dB and the relative band width of 7%, has been developed. The simulation result and measurement result almost agreed well.