Abstract: Based on the field investigation,the interpretation of aerial photographs and the historical data,the magnitude of the Nilk quake on Mar. 8,1812,and its seismologeolog-ical background have been discussed. It indicates that the quake is the result of the dextral overthrust of the kashi River Fault for its main fault distribution and motion character consistent with that of the Kashi River Fault Zone.'The Kashi River Fault is an active fault,which controls the north boundary of the Yili-Basin,and the Kashi River Valley,and it also truncate the Kashi River terrace and the palaeo-Nilk gully,until now it is still in activity. We are found some trails of the palaeo-earthquake in this region. By comparing the variation of the scarps occurred in the quake of 1812,with that of the fault surface occurred in the palaeo-earthquake and its ratio of the fault motion,the present result indicates that the recurrence period of the Nilk quake (M=8) is 1200400 years.