Abstract: In order to solve the problem of signal to noise ratio simulation of GPS intermediate frequency navigation signal, according to the characteristic of the navigation signal, the calculation of signal power and noise power are modified in the signal to noise ratio formula. The signal power and noise power of the signal to noise ratio formula is more close to the real situation, so it can get more accurate signal to noise ratio. Finally, the comparison between the output result of the software receiver and the default value of signal source is made. The simulation results show that the signal to noise ratio accuracy can reach 0.1dB within the range of 36.1dBHz-50.1dBHz for single channel and the signal to noise ratio simulation accuracy is about 0.23dB within the range of 36.1dBHz-48.1dBHz for multichannel. Overall speaking, the new method can be widely used to test the performance of software receiver because the signal to noise ratio simulation method is more accurate than original method.