Abstract: Analyses of twelve characteristic curves by water displacement using in China, Soviet Union and the United States of America. Conception of the methods relating to three types of equation of relative permeability curve includes the basic characteristics of various oil fields. The relationship equation between the cummulative oil production and composite water cut is obtained for every method, so that estimated recoverable reserves can be derived with production data. Seven oil fields with different oil viscosity were selected to compare adaptability of every method and analyze the causes. The forecast methods which are suitable for middle viscosity oil fields in our country have been recommended. Based on the work mentioned before the evaluation of method of characteristic curve by water displacement is given.