Public security, traffic management and service for the people are the three major functions of policing. To assure the quality of police service, which is contingent on the people who render the service, has become the core of policing. Therefore, human resource is one of the most important assets in the police organization. Using samples of the wharf workers in the international harbors and the first-line harbor policemen in Kaohsiung and Keelung, this study investigates the relationships between human resource management practice, human capital, and the quality of police service. It is found that human resource management practice and human capital have positive effects on the quality of police service. It is also found that human resource management practice has a positive effect on the quality of police service through the mediation of human capital. Suggestions and recommendations for future research are thus discussed.