Abstract: Considering manufacturers’ quality decision， the optimal combination between sales contracts and logistics modes for e-commerce platforms is explored. Based on platforms’ operational realities， and taking both sales contracts(direct selling contract and reselling contract) and logistics modes(outsourcing and self-logistics) into account， four combination strategies are constructed: direct selling and outsourcing(strategy DO)， direct selling and self-logistics(strategy DS)， reselling and outsourcing(strategy RO) and reselling and self-logistics(strategy RS). By formulating sequential game models and deriving optimal quality， retail prices and logistics service efforts decisions， the equilibrium results under each format are conducted; further， the impacts of logistics service modes and sales contracts on quality decision are explored. The results show that regardless of which sales contract is chosen， platforms tend to provide delivery services by themselves rather than outsourcing that to TPLS (third-party logistic suppliers). Since providing delivery service by platforms not only benefits both parties but also motivates manufacturers to improve products quality and lower selling prices. Platforms’ optimal combination strategy is closely related to the commission rate， and if the rate is below a certain threshold that is positively related to the quality cost coefficient of products， the optimal strategy is DS; otherwise， the optimal choice is RS.

Key words: e-commerce platform; self-logistics; reselling contract; direct selling contract; quality decision