Cloud computing brings a rapid way for enterprises to launch a new software, which needs lower cost compared with self-purchased infrastructure. More and more enterprises compact their business software as services into cloud platform to the users. In service auction, the service provider aims to make more profits from the service it provides, but the service consumer hopes to select a good quality of service at a low price, which make the relationship of them become one kind of game. In this paper, the game between service providers and service consumers is analyzed. The utility functions of consumer and service provider are respectively established. Then a QoS optimization algorithm based on utility game is designed to solve an optimal QoS strategies to achieve a tradeoff between consumer satisfaction and provider profit. Finally the simulation experiments are implemented by using Matlab platform. The experimental results show that the algorithm can effectively optimize the QoS from two aspects of consumer preference and service cost, which can bring the largest improvement of user satisfaction for service providers with the lowest cost. So it helps to realize a win-win situation between service providers and consumers.