Abstract: In the traditional method,the design of products or the design of parameters in the process planning usually carried out before the design of tolerance.With the development of CADsoftware,engineers can determine parameters and tolerance value without providing the transformational function for circuit analysis.In order to drop the product cost and improve the quality of products,this paper presents parameters and tolerance value and their determination method in the design of circuit.The total costs including quality loss, tolerance cost and failure cost can be minimized and the optimal parameters and tolerance value in a statistical sense can be obtained by using CAD software and response plane method.This shows that parameters and tolerance can be obtained for improving the quality of product and dropping the cost in the complicated early design stage.