Abstract: This paperint roduced the computa tion formula of groundwa ter radon slip changerate, stati stical relation betw een slip chang e ra te evolution and origin time of earthquake occurrence, on this basis, the step of origin time prediction by using groundwa ter radon slip change rate value, judgement index and method are giv en. Combining the earthquake cases, the prediction efficiency is evaluated, resul t indica tes that the predicted origin time rang e is 1～12 month, the average is 5.1 month. This method may apply to mediumand short-term earthquake prediction.

Key words: Groundwater radon, Slipchange rate, Earthquake origin time, Mid-and shor-term anomaly