The paper focuses on quality improvement strategies for manufacturing process. When the manufacturing process is in abnormal condition, managers applied all kinds of quality-improving strategies to keep their product qualities stable. Besides, different quality-improving strategies have very complex relationship between quality costs and revenue. In this paper, we proposed a total expected profit model to find out the best quality-improving strategy. Considering cost under different production equipments, we assumed that the characteristic of products is normally distributed with known mean and variance. Based on optimization technique, the optimal mean and variance can be obtained to optimize the total expected profit. Furthermore, we also develop a numerical example to illustrate the meaning of this research and the result, which could be used by the later researches and actual applications.