It is a popular discount strategy for retailers to sell the same product at multiple prices simultaneously(multiple-price strategy). In order to determine the order quantity of the retailer such that the expected profit is maximized, the classical newsboy problem is extended, and a new newsboy model is established wherein multiple prices correspond to uncertain consumer demand. Two aspects of with and without order quantity constraint are discussed respectively. The Lagrangian multiplier method is applied to solve the order quantity constraint problem, and an algorithm for solving the approximate optimal total order quantity is designed. Numerical results show that the multiple-price strategy is better than a single price strategy, and order quantity constraint has an impact on the choice of the retailers' multiple-price strategy. The retailer's multiple-price strategy is also affected by the price discount coefficient and the difference in demand in the case of order quantity constraint.