This article primarily analyzes the shortcoming in the current formula of plastic and rubber mold shaped dimensions in practical， and fully considered the influence of plastic and rubber contracting fluctuation ratio on the accuracy of the plastic and rubber dimensions. As the introduction of δX sources from mold designers’ estimating error on plastic and rubber contracting ratio or the uncertainty of contracting ratio fluctuation, know that the actual contracting ratio of plastic and rubber fluctuates around the average plastic and rubber contracting ratio. Therefore, the remained measure of repairing mold is the function of plastic and rubber products dimension error δS’ and δS, caused by plastic and rubber contracting ratio estimating error and contracting ratio fluctuation respectively. Based on the probability theory, a comparatively scientific method in calculating the remained measure of repairing mold is proposed. This method exceeds all other Calculating Methods increase design success rate use in Green Product Design.