This paper discusses the retailer-manufacturer Stackelberg model under the background of green supply chain. The manufacturer needs to decide product green degree and the retailer needs to determine green promotion levels. This study considers the optimal decision-making, profit and social welfare of each member of the supply chain under the three decision scenarios: government does not subsidize, government subsidizes manufacturers, and government subsidizes retailers, in order to provide reference for the government to promote the implementation of green supply chain strategies. The results show that government subsidies have a positive effect on the implementation of green supply chains. Moreover, the government's strategy of subsidizing manufacturers will improve the product green degree, social welfare, and the profits of manufacturers and retailers. And the strategy of subsidizing manufacturers is shown to be better through comprehensive analysis. When consumers' preference for green products is low, the green promotion level is highest when retailers are subsidized, but the unit subsidy gain of social welfare is greater when manufacturers are subsidized.