The invention discloses a hydropower station flood discharge gate modeling and calculating method based on a multiple regression algorithm. A flood discharge gate model with three variables includingthe dam front water level, the gate opening degree and the discharge flow is established according to the water level, opening degree and flow relation table of a flood discharge gate; one of the twovariables including the gate opening degree and the discharge flow is calculated according to the other and the dam front water level through the flood discharge gate model for different requirementsof different links of automatic water supplementation. The high-precision calculation of the dam front water level, the gate opening degree and the discharge flow is realized, the high-precision calculation of the dam front water level, the discharge flow and the gate opening degree is also realized, and the model effectiveness and tendency correctness are remarkably improved when the number, correctness and precision of test data are improved.