A group delay model based on trigonometric function series was proposed. And it was theoretically proved that only a finite order of trigonometric function group delay can characterize the influence of arbitrary group delay on signal correlation peaks. On this basis, the trigonometric decomposition series of the group delay were obtained by measuring the correlation peaks and matching the correlation peaks under different combinations of trigonometric function group delays. As a result, the equivalent group delay with similar effects on the correlation peaks was obtained. Simulation results show that the correlation peak of the signal is approximately the same as that of the ideal correlation peak, and the delay estimation error is less than 0.1 ns at different delay time intervals after calibration of the channel by using the group delay estimated by this method.