Making use of FFT/iFFT to realize circular correlation in frequency domain is an effective method for GPS C/A code rapid acquisition. It can help translate 2D Time-frequency joint sliding correlation searching into 1D frequency domain searching, and realize parallel searching for pseudo-code, which can shorten the acquisition time of GPS signal. Meanwhile, the cumulative methods of coherent integration and non-coherent integration which according to the weak signal acquisition are presented, and the test results are given.