This paper studies the impact of sales agent collaborative incentive on a supply chain comprising a manufacturer, a retailer and a sales agent. A collaborative incentive model and a traditional incentive model are established. Two contracts are edsigned by using the principal agency theory, and an analysis is given. The conclusions are as follows: the manufacture's revenue increases; the retailer's revenue decreases; but the revenue of the whole supply chain increases. Moreover, the sharing coefficient of the retailer from the manufacturer and the commission of the sales agent from the retailer decrease; the change of the sales agent's salary is determined by the risk aversion parameter.