Abstract: A loop-shift Stop Go adaptive digital filter with applications in period detection and signal separation of overlapped periodic signals is presented. The filter places no contraints on the overlapped forms and requires no priori knowl edge except for approximate period range for signals to be separated, therefore it provides for an efficient and feasible method for separating periodic signals overlapped both in time and frequency domains. The convergence speed of the filter and the requirements of all parameter selections are discussed,meanwhile thecoarse precision period search and channel automatic close algorithm are proposed to reduce the amount of computation. Experiments show that the filter can separte all kinds of overlapped periodic signals with different initial phases and different relative magnitudes.