Abstract: This paper analyses the characteristics of long-nd medium-termsei smicity on China's mainla nd. We selected earthquake catalogue on North china seismic region and South-North seismic zone from 1970. 1 till 1997.12. After removing the dependent earthquakes, we have found that all earthquakes, either North china seismic region or Southnorth seismic zone, from ML 3.0 or ML 4.0, the feature of residual earthquakes shows clustering. And the long-term variation of seismicity is governed by power lawtemporal distribution; it is scale-inv ariant. The fractal dimension of shallow earthquakes on china mainland changes from 0.2～0.7.

Key words: Fractal, Earthquake catalogue, Clustering, Scale-invariance