In the context of green development and increasing green demand, consumers' perception of greenness and freshness in agri-food product will affect their purchasing decisions. Blockchain is being looked at as a technology that can build trust between consumers and the greenness and freshness of product. To stimulate the development and application of blockchain technology, the Chinese government has put forward some subsidy strategies, this will have what effect on enterprises' blockchain investment decisions, and what are the investment rules? To study these issues, we chose a green agri-food supply chain (GAFSC) with one producer, one blockchain-based traceability service provider (BBTSP) , and one retailer as the research object. Assume that the government offers a tax subsidy strategy to the organizations of blockchain usage and R&D. Then, considering the perceived credibility of consumers on product greenness and freshness after using the blockchain technology, the demand function was revised. Furthermore, we proposed and analyzed three subsidy models. Findings: 1) When the blockchain technology investment cost of the BBTSP can meet a certain range, the benefits of supply chain stakeholders in the tax subsidy conditions will be higher than those in the no -tax subsidy model. In addition, the BBTSP's blockchain technology investment cost has a negative relationship with the tax discount coefficients of the BBTSP and the producer. 2) All supply chain members getting tax subsidies from the government cannot always increase their incomes, and this is in contact with the tax subsidy rates and the blockchain technology investment cost of the BBTSP.