Abstract: Acquisition of C/A code is most important for GPS receiver in weak signal environment. Processing coherently with long integration time is an efficient way to improve the sensitivity of GPS receiver. However, because of the transition of the navigation data bits, the integration time has to be limited. How to detect the transition of navigation data bits is the key issue to prolong the coherent integration time in weak signal environment. In this paper, some conventional acquisition technologies are studied carefully and the idea of optimum path is introduced. Optimum path algorithm is employed to minimize the cost function which determines the transition of navigation data bits. Furthermore, the whole acquisition algorithm based on the optimum path is given. This novel algorithm process the received data coherently with longer integration time and without any squared loss. Compared with other algorithm, the new method can reduce computing burden dramatically. The acquisition rate expression is also deduced. Simulations show that the new algorithm can effectively improve the acquisition rate. When integration time equals 80ms, SNR equals -40dB, the new optimum path algorithm still has as high as 92% acquisition rate which remarkably improves the sensitivity of GPS receiver.