Abstract: The Flood prevention characteristic water level is an important basis for flood warning and flood prevention decision-making, which directly affects flood prevention dispatching and dike inspection. In view of the current situations of flood prevention projects and riverbed changes in the main stream of Daying River and Ruili River in Dehong Prefecture, Yunnan Province in recent years, the unreasonable problem of high characteristic water level standard is exposed. This paper analyzes the necessity of adjusting the characteristic water level of the main stream of Daying River and Ruili River. According to the adjustment principle and determination method, the warning water level and guaranteed water level of the control station of the two rivers are revised.