In 2007, Chen and Liu's model presented the optimum profit model between the producer and the purchaser for the supply chain system. However, their model did not consider the used cost of customers in pure procurement policy. In this study, the author proposes a modified Chen and Liu's model with normal quality characteristic of product for determining the optimum process mean and order quantity. The optimum purchaser's order quantity and the producer's process mean will be jointly obtained by maximizing the expected total profit. Taguchi's symmetric quadratic quality loss function will be applied in evaluating the product quality.