Abstract: A Bayes discriminant analysis and a x²-test for earthquake precursory identification are applied to the radon data obtained from 1990 to 1998 at 10 observatory stations in North China in the paper.The anomalies of radon are obtained and used for the tests in retrospect and extrapolating forecasts of medium and stroneg earthquakes in the region.When the risk level K_dn=4 is taken,5 in 7 earthquakes can be correctly identified during the retrospect time.The forecasting time interval is 33% of the total and capability of forecast R=0.38;1 in 2 earthquakes,the January 10,1998 Zhangbei Earthquake with magnitude 6.2,is correctly forecasted during the extrapolating time,in which the forecasting time interval is 5% of the total and R=0.45.R=0.40 can be obtained during the whole time interval.