According to the question of whether corporate social responsibility (CSR) enhances the product quality provided by supply chains, a two-stage game model in a supply chain consisting of an upstream manufacturer and a downstream retailer is built to investigate how the manufacturer’s CSR affects the equilibrium operating results of the supply chain. The results shows that：an increase in the degree of the manufacturer’s CSR increases the product quality, the product demand and the stakeholders’ economic profit, but reduces the manufacturer’s economic profit; the product quality, the product demand and the stakeholders’ economic profit increase with the product quality improvement efficiency, but how the manufacturer’s economic profit changes depends on the relative size of the degree of CSR and the quality improvement efficiency. A proper combination of a quantity discount contract and a quality improvement cost sharing contract can effectively coordinate the operations of the supply chain. The CSR activity implemented by the retailer leads to a higher product quality level and a higher product demand.