Abstract: We have analyzed comparatively the optimum pricing of dividing up demand interval equally and pricing of fixed discount ratio on the aspects of division of interval and the consumer's surplus which be gained by a monopoly enterprise. The conclusions are as the following:the demand interval will be divided up by this means that a front interval is longer than a hind interval (the first interval is exceptional) if we price under fixed discount ratio; the two pricing method will both make a monopoly enterprise gain equal consumer's surplus on the whole.