Concerning the problem that conventional chaotic array used for detecting track frequency-shift signals with low frequency information is of high complexity and low accuracy,we propose a low frequency signal detection method based on variable step paroxysmal chaos to improve the conventional methods.Through setting a sequence of steps which can cover the frequency band of the low frequency to be measured,we use one Duffing oscillator to accomplish track low frequency detection.In conjunction with the advantages of the Duffing chaotic system in signal detection,we analyze the feasibility of using variable step paroxysmal chaos to detect low frequency,describe the detection steps,and theoretically calculate the step sequences which can cause paroxysmal chaos.We build a simulation model on the Matlab/Simulink and the simulation results show that the proposed method is feasible.Finally we further study on the simulation results using the period method of paroxysmal chaos and obtain accurate low frequency signals.The detection method based on variable step paroxysmal chaos outperforms the traditional track low frequency detection method in accuracy and system complexity,and it can achieve low frequency signal detection under low signal-to-noise ratio.