Abstract: According to receivers dynamic environment, high dynamic GPS signal simulator can precisely generate GPS signal that the receiver get. GPS signal simulator has many technology request, the intensity of the signal is a key technology in the high dynamic GPS receivers research and development. After the GPS signal is demodulated, the Signal Noise Ratio(SNR) of the receiver is analyzed in this paper. On the basis of above, the paper also derives how the signal generated by GPS Signal Simulator reflects truly the GPS signal and outside noise. Experimentation result proves the effectiveness of the method mentioned above.