Aiming at the problem that the performance of RF SAW sensor with small size is influenced significantly by the package, a simulation method combing the couplingofmodes (COM) model and the 3D electromagnetic analysis has been presented in this paper. First, the single port S parameter of the chip was calculated by using COM model. Then the model of the ceramic package structure with surface mounting is established by using the high frequency structure simulator (HFSS) and its S parameter is calculated. Lastly, the simulation results of SAW resonant sensor considering package are obtained by combining the S parameters of the chip and the package structure in ADS software. The SAW single port resonant sensor operating at 428.5 MHz has been fabricated experimentally. The simulation result obtained by using the method described in this article is more close to the experimental results, which verified the feasibility of the abovementioned method.