This article focus to Discuss on Police Systems. Here briefly discuss on Federal police agencies, like the Federal Bureau of Investigation (FBI), the Bureau of Alcohol, Tobacco, and Firearms (ATF), the Drug Enforcement Administration (DEA), the U.S. Marshals Service, the Secret Service and the Immigration and Naturalization Service (INS). This article also explain Internationalization of law enforcement. Finally analysis State police, County police, Municipal police and there characteristics.