Through the field investigation in Weihe River, three layers of palaeoflood slackwater deposits in the loess-paleosol profile were found， which are reliable archives of the palaeoflood events. The post-IR SAR protocol was applied to nine samples to reconstruct the chronology framework of the palaeoflood events in the middle reach of Weihe River. The results show that the middle reach of Weihe River has a flood-prone during 3.2~3.0ka. and three large flood events are recorded. The OSL ages of these large flood events are 3.2±0.2ka、3.1±0.3ka. and 3.0±0.2ka., It indicated that the unstable climate environment from Holocene Megathermal Period to the late Holocene lead to the breakout of palaeoflood events.