Abstract: The process of offset plate copy is controlled through the correct reproduction atthe highest andthelowest tone .Based onthe offset control strap,this paper proposes a newdetected method of plate resolution and analytic method of the correct copy range of plate .Using these methods and through the experi ment . The authors analyze the resolution andthe correct copy range of three types of offset plates .By workingin the correct copy range .The authors can guarantee the consistence of tone reproduction of different types of plates .This is the precondition for color consistence in color printing and convenient to adjust thepress .