Abstract： Research purposes: Traditional Duffing oscillator has small frequency parameter restriction， and the detecting angle caused by initial phase angle and the detection results are only qualitative judgment in detecting ZPW - 2000 shift frequency signal. In this paper we make improvements in detection method and get an improved Duffing oscillator detection system. Research conclusions:(1) The detection model of any frequency signal is obtained by using the general time scale transformation to traditional Duffing equation. (2) Bacause the initial phase angle may make the detecting blind angle in the measured signal，the detection blind angle is eliminated by making the original driven signal phase shift a degree. (3 ) In order to obtain the accurate detection results，on the basis of the qualitative judgment of the phase diagram and time domain diagram， a quantitative method based on the detection statistic is proposed to realize the accurate determination to the detection results. The simulation obtains that the detection accuracy of this method is higher than qualitative judgment. （4) The improved Duffing oscillator detection system is first applied to the detection of ZPW -2000 shift frequency signal. The steps of detection are given. The simulation results show that the detection system of improved Duffing oscillator can realize the detection of ZPW -2000 shift signal in low SNR. (5) The research outcome will realize the accurate detection of ZPW -2000 shift signal in background of strong noise.