This paper is aimed at the flood-control expert system for the middle reaches of the Huaihe River. The highest and lowest water levels are adopted to quantize the semantemes. The semi-normal distribution fuzzy function is used to calculate the confidence factors. The calculation is based on the simulated results of methodology-base. The fuzzy classification is used to transfer the confidence factor of one state into another. The suitability and practicality of the above methods have been verified and validated by simulating decision-making of flood-control for many times of historic floods in the middle reaches of the Huaihe River.