Abstract: Based on digital signal processing method, the gas radon data of Liaogu-1 Well in recent two years are filtered, and its potential cycle is picked up with spectral analysis.The results show:besides the annual cycle, there are a 12 and a 24 hour short cycle and a 1~2 month moderate long cycle in the data.It indicates that digital signal processing technology is useful in the precessing of seismic precursory data.