Surface acoustic wave(SAW) devices are sensitive to surface contamination and therefore, their surfaces are protected by using special packages. These packages could bring parasitic into the SAW filter that has an significant affect on its performance. In this work, we have designed a SAW duplexer implemented by using wafer level packaging(WLP). The aim of this work was to minimize the parasitic influence caused by WLP packaging with ADSmomentum software. The simulation results suggested that differences in packaging design could have a significant impact on the filter’s isolation and rejection. A few modifications on the package’s pads and layout could improve the filter’s band rejections by 57 dB. In general, this work had provided the foundations for future works on WLP packaged SAW devices.