Based on the available literature and data of U.S. census bureau, this article systematically studies the history of the development of the county in American, American county models, vast variations in size and population, powers and duties and traditional forms of county government; emphatically summarizes the reasons why counties confronted crises while the industrial society came and solutions for the problems; finally explained mechanism that the importance of counties in post-industrial society is increasing and implications for china's county government reform.The U.S. county system as a unit of local government was originally created to serve as administrative arms or political subdivisions of their state governments in the rural society. County boundaries in most states were generally laid out during the pre-automobile age so that the distance a man could travel on a horse in half a day determined the size of the county with a view to allowing reasonably convenient access to the courthouse. However, there were a lot of obstacles and objections to the reform of county government and widespread county consolidation because of inadequate area and antiquated structure and the continuing population decline. During the era of suburbanization, technological, social, and government changes acted in concert to encourage the movement of population and employment to the edge of the old city and beyond. In the meantime of continuing population growth in the United States, many counties were experiencing increases. These are the background and circumstances where American county governments have been "found" or "rediscovered". Moreover because county governments have area-wide jurisdiction (that is, legal authority over the entire county that supersedes states grants of power to other units of government) as well as linking and coordinating capabilities, they are the logical choice to deliver many of "regional" or "urban-type" services in metropolitan regions.