Abstract: Flood disasters have occurred for several times in the lower reaches of the Weihe River since recent 30 years and resulted in enormous destruction. It is more and more necessary to deeply research the occurring laws of flood disasters in the study area. In this paper, the change in flood disasters during the period from 170 BC to 1992 AD was analyzed based on the historical flood disaster records in the lower reaches of the Weihe River. The results show that 243 flood disasters were recorded in the lower reaches of the Weihe River, in which they occurred less frequently before 630 AD but more frequently after that. From 1920, flood disasters occurred more and more frequently, but they reduced to some extent  after 1960. According to the historical data, fluctuation of the occurring frequency of flood disasters could be divided into 7 periods, the relationship between flood disasters and entironment evolution was analyzed, and the results show that the occurrence of flood disasters during the historical periods was directly related to the entironment evolution in the drainage basin. Therefore, it is very important for reducing flood disasters to intensify the entironment construction in the drainage basin.

Key words: historical period, flood disaster, frequency, entironment, Weihe River