The invention discloses a water quality mechanism modeling and water quality prediction method based on a fruit fly optimization algorithm, belonging to the technical field of environmental engineering. At first, the invention combines the water quality evolution mechanism, and proposes a lake reservoir water quality mechanism modeling and water quality prediction method based on a fruit fly optimization algorithm. Based on the known water quality measurement data, the unknown parameters of the water quality mechanism model are estimated by using Drosophila optimization algorithm. On this basis, the water quality evolution process is predicted by Monte Carlo simulation, and the probability distribution of water quality indexes in the future is obtained, and the water quality prediction isrealized. The invention can establish an accurate water quality mechanism model, and the water quality mechanism modeling method based on the drosophila optimization algorithm can accurately estimateunknown parameters of the water quality mechanism model, which improves the optimization accuracy and speed compared with the prior method; water quality prediction method can effectively realize water quality prediction, and consider more comprehensive, accurate, and overcome the contingency of single-value prediction results.