Reishui-Riyue Mt. active fault zone is a very important NNW oriented right-lateral strike-slip active fault zone which developed in the Chaidam-Qilian Mt. active crustal block, northeastern margin of Qinghai-Tibet Plateau. The activity of the fault causes a series of micro-geomorphologies, such as ridge, valley and terrace, right-lateral offseted and forms fault cliff and fault scarp et al. vertical offset micro-geomorphology. In this paper, the palaeo-earthquake events on the fault are studied. Combining the trench profiles and fault scarp measurement, two palaso-earthquake events are determined, which occured in 6 280 ±120 a B. P. and 2 220 ±360 a B. P., the recurrence interval is about 4 000 a.