Abstract: In order to extract the effective prediction index for moderate-strong earthquakes in the northwestern margin of Ordos block, small earthquake activity windows of different magnitudes and ranges are analyzed in Yinchuan area, a seismic window with predictive significance is selected by calculating the R value and molchan test. The results show that the seismic activity of M_L4 Yinchuan window has a good indication for earthquakes with magnitude ~ 6 in the northwestern margin of the Ordos block. When the annual frequency of M_L3 seismic activity of the Yinchuan seismic window is greater than 2, it has a good indication for the occurrence of earthquakes with magnitude greater than or equal to 5 in the northwestern margin of the Ordos block in the next year.