The simulation and design of SAW low loss ladder filter with 42°Y-XLiTaO3 substrate have been carried out by using COM and 〖WTHX〗P〖WTBZ〗 matrix cascading technology. By analyzing the impact of SiO2 layer thickness on the center frequency deviation of filter and establishing the equivalent circuit model to simulate the package, a 4 order SAW ladder filter with the out of band rejection of more than 20 dB and the insertion loss of less than -1.2 dB at the center frequency of 1 575 MHz has been designed. The simulation result and measurement result agree well.