Abstract: In this paper, the data of flood alarm of Yellow River in Qing dynasty, the drought and flood distribution of China in recent 500 years, etc. are used to estimate the series of natural annual runoffs from 1470 to 1918 for Sanmenxia gauge station of Yellow Rivers, which consists of a series of 520 years natural annual runoffs with the 71 years observed data from 1919 to 1989 of Shanxian (Sanmenxia) gauge station.