In this paper, taking the origin times of earthquakes with different magnitudes, which occurred in different areas of North-South Seismic Belt as samples, the GM (1,1) building model method of the grey theory is used to build 13 prediction models.Using these models, the origin times of coming earthquakes have been predicted.The origin time of Guyuan M5.0 earthquake, Ningxia on Nov.2, 1989 was predicted betterly using the model with 5.0≤M≤5.9.