Abstract: The product quality has always been a hot academic issue. However there is a wide gap between the situation of product quality and the consumers' growing demand. Quality accidents not only show that the enterprises do not have strong sense of quality, but also reveal the poor efficiency in product regulation. Governments and the third-parties are two important bodies of the product quality regulation, however previous research just proposed the importance of the third-parties, the relationships and behaviors were less considered between them using the quantitative method.
Under limited reason conditions, the model of governments and the third-party is constructed based on the evolutionary game. Game analysis shows that the governments' incentives and regulation cost as well as the penalty of the third-party is the critical factor which affects the evolutionary stable strategies. The effect of those critical factors is also discussed by numerical simulation with the variations of the different parameters. The results show that it is helpful to regulate the third-parties by lowering the regulatory costs of governments, increasing subsidies for the third-parties and the punishment of the third-parties's illegal behavior. Finally valuable and practical suggestions are provided for governments to guide the behavior of the third-parties towards the excepted evolution direction.

Key words: government regulation, the third-party, product quality regulation, evolutionary game