Abstract: The definition of the weak signal and the influence factors are discussed.In order to acquire the weak signal,a high gain must be gained,and a long integration time is needed.As regards the long integration time,the most challenging problems are navigation data transitions,Doppler frequency errors square loss caused by non-coherent integration.In high dynamic weak signal environments,the balance of the integration time and Doppler compensation must be considered.After analysing those,FFT acquisition has more superior than traditional ways.Different coherent integration can improve the integration time and remove square loss very well.The half-bit method with the estimation of bit transitions can well estimate the bit transitions.Code Doppler compensation must be done in high dynamic weak signal environments.An improved weak signal acquisition method is proposed and simulation results prove the proposed method by means of Monter Carlo.