Among optimal control methods of icestorage air conditioning, control methods based on intelligent optimization algorithms are complicated to solve and lack of feasibility, and common engineering control methods are of poor economic benefit. To solve the above problems, in this paper, the mathematical model of the icestorage air conditioning optimal operation is built, in which the capacities of operation patterns and icestorage capacity are constraint conditions, and the minimum daily operation cost is the objective function. Then, an optimal control method based on the sequential reduction in direct cooling cost is proposed. Periods of storing or melting ice can be planned according to the arrangement of electricity price and direct cooling cost. Through several iterative computations, an optimal solution can be found. The proposed control method is of certain reliability by making a comparison with the optimal result obtained by GAMS. Compared with common engineering control methods, the proposed method has good feasibility and economical efficiency.