Abstract: Location privacy protection is arising people’s more attention and research.Currently location privacy-preserving based on users of mutual cooperation without a central server is now the focus of the study．In order to better protect the privacy of the user’s location in real untrusted environment, this paper provided a location privacy protection method Privacy_l which is based on the idea of user collaboration game．Anonymous group is formed by users collaborate,density center of anonymous group as the anchor instead of the true position to initiate the query.To calculate the anchor through secure sum,this method could eliminate the situations that do not cooperate in good faith in real implausible circumstances.Meanwhile,according to the users’ different location-privacy requirements,different anonymous protective effect is achieved by setting different levels of privacy protection parameters.In addition improved incremental query method is used to improve the efficiency of nearest neighbor queries．Simulation results show that this method has better performance,and can be applied to reality better.

Key words: Game,Collaboration,Location privacy,Privacy-protection