Abstract: BP neural network is used in mid-term earthquake predietion.Some usual predietion parameters of seismology are used as input units of neural networks.And the output urits of neural networks are called as the characteristic parameter W1 deserlbing enhancement of seismieity.It is used for spatial seanning in North China.The result shows that the mid-term anomaly zone of W1-value usually appears obviously around the epleenter about l～3 years before future eearthquakes with good predietion effeet.

Key words: BP neural network, Nonlinear relationship, Enhaneement of selsmieity, Mid-term earthquake Predzetion