Abstract: With the increasing awareness of environmental protection, the green travel is getting more and more attention. However, in terms of the green car rental, there are few studies on the cooperation mechanism between the green car rental company and the city government. Therefore, this paper will study the relationship between them by applying the supply chain coordination contract theory.
Firstly, considering a two-echelon system which is composed of a green car rental company and a government, the game model between them is built with the assumptions that the demand rate is random and depends on the government's promotion efforts. Secondly, the optimal decisions of fleet sizing and promotion effort level under the decentralized decision, the centralized decision and a combined contract based on revenue sharing and cost sharing are researched respectively, and a comparative analysis is carried out. Finally, the example analysis is employed to verify the reliability and validity of the above models.
The following results is attained:the system can't achieve coordination under the decentralized decision; the introduced combined contract of revenue sharing and cost sharing can not only achieve system coordination but also make the members of the system achieve Pareto improvement when the contract parameters satisfy certain conditions. The example analysis illustrates that the two parties can achieve the integrated optimal profit only through cooperation. the proposed cooperation mechanism between the green car rental company and the city governmentcan provide an innovative theoretical basis for further related researchs.

Key words: green car rental, fleet sizing, promotion effort level, revenue sharing and cost sharing