Abstract: For a supply chain consisting of a green manufacturer, an online platform, and an offline retailer, considering the scale differences between the online platform and the offline retailer, game models are constructed under the scenarios where the green manufacturer does not provide value-added services, provides value-added services only for one party, and provides value-added services for both parties. The optimal value-added service strategy of the green manufacturer and its impacts are studied. It is found that: (1) It is beneficial for the green manufacturer to provide value-added services. When there is a large scale difference between the online platform and the offline retailer, the green manufacturer should provide value-added services with the same service level for both parties; otherwise, it should provide services only for the online platform. (2) It is always beneficial for the online platform to accept the value-added services provided by the green manufacturer. Whether the offline retailer accepts the value-added services depends on the scale difference between the online platform and the offline retailer. Through model expansion, the impacts of consumers' green preference and the cost sharing between the online platform and the offline retailer on the choice of the green manufacturer's value-added service strategy are explored. It is found that: (3) As consumers' green preference increases, the green manufacturer tends to provide value-added services with the same service level for both parties. (4) When the online platform and the offline retailer share the cost for the green manufacturer, the choice of the green manufacturer's value-added service strategy is affected by the scale difference between the online platform and the offline retailer and the cost sharing rate.

Key words: Value-added service strategy, Channel competition, Scale difference, Green Supply Chain.