Abstract: In a three-level supply chain consisting of battery suppliers, new energy vehicle manufacturers, and retailers, the optimal pricing for supply chain members, the innovation level of battery suppliers, and the sales effort decisions of new energy vehicle retailers are analyzed under centralized and decentralized decision-making models. A joint "cost-sharing and revenue-sharing" contract is proposed to eliminate the double marginalization effect in decentralized decisions. Numerical analysis is used to examine the impact of parameters such as the overall transaction price on innovation, sales effort, and profit, as well as the effectiveness of the joint contract. The results show that profit and innovation levels are positively related to the overall transaction price and negatively related to the innovation cost and sales effort cost coefficients. It is also found that, under certain conditions, the "cost-sharing and revenue-sharing" contract can lead to Pareto improvement in the new energy vehicle supply chain.