The invention provides a cooling load prediction based optimal control method of an ice-storage system. The method comprises the steps as follows: step one, total daily cooling load amount of an object of the ice-storage system is predicted; step two, whether the total daily cooling load amount of the object exceeds a proportion of total cold accumulation amount of the required ice-storage system is judged, if yes, a step three is executed, otherwise, the ice-storage system adopts a partial cold accumulation mode for cold supply, and then a step four is executed; step three, a corresponding cold accumulation mode is adopted for cold supply according to a priority level sequence of electricity price periods; and step four, during the electricity price valley period, the ice-storage system performs cold accumulation according to maximum cold accumulation power, and all cooling load is provided for the system by the cold accumulation amount. According to the invention, the method based on cooling load prediction and priority ordering is adopted to optimize a control strategy of the ice-storage air-conditioning system, and the economic efficiency of the operation of the ice-storage system is improved.