Seismogenic process of west to Kunlun Mountain Pass M_S 8.1 earthquake is consists of three evolutionary stages for seismicity pattern. The first stage is background gap formed by M_S ≥ 6 earthquake from 1959; the second stage is pregnant gap formed by M_S ≥ 5 earthquakes from in 1994, and the third stage,"imminent earthquake gap" lasts 4 months before the M_S 8.1 earthquake. At the later period of the pregnant gap, seismic bands in 1~2 years appeared in Qinghai-Xizang block and western China. Along with the formation of the "imminent earthquake gap", no small earthquake occurred in the region. The time-space evolutionary feature of M_S 8 earthquakes in western China is discussed at the end.