Abstract: The promotional pricing of seasonal commodities is studied taking account of their sales characteristics, discount rates, inventories, cyclical slump, real price, and so on. A dynamic pricing model is thus developed to minimize the loss of profit on a restricted condition that the volume of goods is needed to sell off. By the genetic algorithm and particle swarm, a pricing is given with optimal cost. The effect of pricing on loss of profit is analyzed through a simulation so as to provide an important reference for promotional decision-making in large/middle-scale companies.