A method for dispatching a power system based on optimal load transfer ratio and optimal grid connection ratio of wind power and photovoltaic power includes: acquiring load data; drawing a load curve; defining a peak load period, a flat load period and a low load period, and calculating average loads of the peak load period, the flat load period and the low load period before a load transfer; determining value ranges of a peak-low load transfer ratio, a peak-flat load transfer ratio and a flat-low load transfer ratio; establishing an objective function considering generation cost of thermal power unit, wind power purchase cost, PV power purchase cost and compensation cost for consumer load transfer; introducing an immune algorithm to calculate grid connection ratio of wind power, grid connection ratio of PV power, peak-low load transfer ratio, peak-flat load transfer ratio and flat-low load ratio corresponding to a minimum operating cost.