Towards the development of city, the security becomes the key spot which is paid attention by each community. Therefore, the 110 police cars are deployed and patrol in different streets in order to guarantee social security. In this paper, we firstly introduce the Police Cars Deployment Model with the index of police vehicles, line coverage rate, line repetition rate and point coverage rate. Three algorithms: Flooding Algorithm, Hierarchical Cluster Analysis and Genetic Algorithm are introduced to give approximate solution. Moreover Police Cars Patrol Model is built imitated Brownian Molecular Motion to introduce collision probability. At last, the models are implemented and the sensitivity analysis is given.