Abstract: Under the non-cooperative game, vendor and purchaser decide optimal lot size according to their own interests. One may be in an optimal condition, but the whole supply chain is not. To optimize the whole supply chain and attain the win-win goal, mutual optimal lot size models and the quantity discount pricingmodels were proposed under the cooperative game. The price discount can be determined with the models and by taking the bargaining powers and contributions of the both sides into consideration.