Abstract: The direct acquisition method of P code is researched for the receivers under low SNR and high dynamic environment. The method uses non-coherent integration and Tong multiple trials with the position constraining of peak value to increase the detecting ability for weak signal. An improved searching strategy is put forward for adapting the environment of high dynamic by dividing time domain. Then the method parameters are optimized for one special application, including detecting probability, false alarm probability, non-coherent integrating times, Tong judging parameters and separated blocks number of time domain. Tests show that the improved strategy can reduce the probability of missing detection by 30%, even under the condition that received signal power is just -133dB(mW), the moving velocity is 900m/s, the acceleration is 20g and the time uncertainty is ±1s, the false alarm probability is less than 10^-7, the detecting probability is over 90% and the acquiring cost time is shorter than 50s.