Abstract: Workers are key factors that affect product quality in process. Because of the asymmetric information between enterprise owners and their workers, with postverification feature of quality and not-easy-to-monitor process details, workers tend to focus on quantity and selectively ignore quality. Based on the asymmetric information theory, a principalagent model of product quality in process between enterprise owners and their workers is established and discussed from the perspective of economics and the effective ways to motivate workers in quality improvement, and finally several suggestions are given on how to promote the model's using in practice.