Considering the thermophysical properties and price of insulating material, the structure and requirements of a cold storage, the type of insulating material was selected by the method of fuzzy multiple judgement, the thickness of the insulating layer was decided by the method of economical thickness which was based on economic benefit. Therefore the sum of the initial investment, the operating cost and the drying loss cost was reduced to a minimum. MATLAB 5.3 was used to optimize the design of insulating material. The economical and reasonable results were obtained.