Abstract: An optimization dual model was developed to minimize the cost of Compound Fertilizer. The model was used to illustrate the bidirectional effects of both raw material and constraints, especially when the price of raw material was changing rapidly. The most economic formulations were calculated by Lindo 6.0. The reason for raw material unadopted was that their effective components were not matched to price by Reduced cost analysis. The influence of adoptive raw materials was discussed through Sensitivity analysis, and the phosphorus was the most sensitive factor in actual formulations. The sequence of three main elements' shadow price was K>P>N, which indicated the Potassium influenced the total cost mostly.