Experimental design has been used as a scientific method to improve the quality. This method omits the quality problems basically and creates the improvement really.Taguchi, an experimental design method, is a practical and strategic method which has been used to design quality for products and manufacturing or service processes. This methods has been used in most of developed countries successfully.This method of solving quality problems acts powerfully to improve process turnover and make productivity with reducing unconfirmed products ,reworking cost and variation especially in manufacturing section. In this study taguchi method by way of using overall evaluation criterion (OEC) was performed in rooz nosh kermanshah factory to achieve two goals, reducing deviations of acidity and pH from target value simultaneously.This method among 5 factors (A, B, C, D, E) which seemed have important effects or interaction effects sifted 4 factors (A, B, C, E) .Next this method gave a solution by setting those 4factors in optimum levels (A1, B1, C1, E2) .Set of these factors in their optimum level has increased S/N ratio about 2.402 unit which proportion of each factor is respectively 0.404, 0.613, 0.832, 0.552 and overally has rised S/N ratio from -35. 963to 33.545.