Radon in groundwater of the Dongxia spring was put into observation in 1987,and its data were continuous and reliable.Based on the judgement of data anomaly by using nonlinear regression and hydrochemically practical processing method,the anomaly that exceeds the annual dynamic value by two times residual standard deviation can be regarded as seismic anomaly.The radon data have shown obvious anomaly reflection before the earthquakes around the boservation station.