Abstract: In order to achieve bit synchronization of high-dynamic and weak GPS signal, a bit synchronization method based on differential coherent accumulation is proposed, called differential accumulation method. With this method, every one of complex samples after coherent integration within a navigation data bit period is multiplied with the conjugated of the previous corresponding sample that the interval between them is an integer number of navigation data bit length and the product is accumulated, and then non-coherent accumulated as a statistic to calculate the value of the 20 candidate locations, the starting position of differential coherent accumulation corresponds with the largest value is determined as navigation data bit boundary position to perform bit synchronization. Simulation results show that the differential accumulation method is suitable for high-dynamic, weak GPS signal bit synchronization.