An adaptive acquisition algorithm of PN codes is presented based on SNR control because the acquiring SNR is time-varying in complex electromagnetism environment. The use of the algorithm can reduce the mean code acquisition time and the virtual alarm probability. Based on the performance analysis of the sliding correlation method, an adaptive scheme is constructed to achieve the goal to set the time of integral and the threshold in SNR control, and the influence of the above parameters on the performance of acquisition is studied as well. Simulation results show that the method can reduce the mean code acquisition time by 50% when SNR>-3 dB, and reduce the virtual alarm probability by 5%~35% when SNR<-7 dB, the method meets the design requirements of acquisition properties under the SNR change environment.