Abstract: In this paper all-phase digital filter with double windows in frequency domain is presented first, through theoretically analyzing, then the according FIR system and the condition for linear phrase are given, which has apparent transmission property and waves in pass or stop band basically disappear, and it’s easily to make complementary sub band filter bank using all-phase filter. Signals added by noise are processed N times in the all-phase spectrum normalization way. It is recursively to set frequency point with amplitude 1 so to form the whole transmission property H. Noise is judged by the mean and variance of single and all-phase spectrum analysis. In the test, the drowned signals in the noise are processed using all-phase adaptive filter. The result verifies that signals with frequency by n times of spectrum resolution can be recovered 100% without lost. Signal quality are improved by 0.8dB, which can be further raised by means of increasing N or correcting spectrum.