Abstract: Radar through wall detecting is a kind of new technology of exploring.In this paper，a continuous-wave low-complexity dual-frequency Doppler radar and the basic algorithm for detecting moving targets behind barriers is present briefly.After analyzing the main characteristics of the algorithm，A ARMA（Auto-Regressive Moving Average） model is introduced to improve the poor resolution which is one of the main drawbacks of the traditional Doppler radars.Simulate the imaging results，including both the traditional algorithm and the ARMA-based algorithm circumstance.Comparing the results，the efficiency and the priority of the new algorithm is proved.