The supply chain equilibrium model is constructed by means of bi-level programming. The coordination model of pricing decision is studied, and the price discount contract as a coordination mechanism is presented. A supply chain model with a leader and three followers is then constructed. The study shows that the bi-level programming can simulate the stackelberg game, and price discount contract can coordinate with the supply chain At last, the previous model is simplified to a new supply chain with a leader and a follower; and then the relationship among the wholesale price, retail price and discount rate is obtained. The analysis can be guidance to make decision on supply chain price with stackelberg game.