The invention provides a method for controlling the discharge rate of a gate automatically. The method comprises obtaining hydrology monitoring data so as to obtain the real-time inflow rate of a river channel, obtaining the variable condition of the real-time flow of the river channel according to the real-time inflow rate of the river channel, obtaining the lift of a porous gate by adopting a neural network model and according to the variable condition of the real-time flow and the requirement of the discharge rate of the river channel, and controlling the unlocking of the gate according tothe lift. The method of the invention integrates the characteristics of fast calculation speed of a single-dimensional hydraulic model, high calculation accuracy of a two-dimensional hydraulic model and intellectualization of the neural network model, therefore, the method guarantees not only the immediacy but also the accuracy, and effectively combines a hydrology model and the hydraulic model onto a unified management platform.