To explore the optimal government subsidy strategy for a green supply chain (GSC) under behaviour-based pricing (BBP), three types of GSC subsidy models under BBP are explored by using game theory, and the influence of different subsidy ratios and subsidy coefficients on pricing and greenness under BBP was analysed for the first time. Additionally, the effects of different strategies are compared. Our results reveal the following: First, when the subsidy is based on output or green degree, the proportion of green product retailers receiving subsidies has only a positive impact on the wholesale price of green products. Second, when the product R&D input cost is subsidized, the proportion of green product retailers receiving subsidies is negatively correlated with greenness, wholesale price, loyalty price, poaching price, market share of green products and GSC profit. Third, when the product R&D input cost is subsidized, the loyalty and poaching prices of green products always increase with an increase in the subsidy coefficient. However, when the subsidy is based on output or green degree, the loyalty and poaching prices of green products increase or decrease with the increased subsidy coefficient. A numerical case example shows that the optimal subsidy strategy of a GSC under a BBP is different from those of previous studies. Subsidies based on green degrees are the optimal strategy for green product retailers, green consumers and governments.