Abstract: Based on the reality that most enterprises incorporate CSR into their strategic planning, the impact of manufacturers'CSR investment mode on supply chain members and system profit is studied. Three investment modes are considered: manufacturers do not invest in CSR (model NN), the single manufacturer invests in CSR (model NY), manufacturers both invest in CSR (model YY). The equilibrium price and profit are obtained by establishing a two-level supply chain model of competing manufacturers and a single retailer. The study shows that the manufacturers' profits are always inversely proportional to the price sensitivity coefficient, but only in the model YY, the retailer's profit is directly proportional to the price sensitivity coefficient. Moreover, when both manufacturers invest in CSR, all supply chain players can maximize profits and achieve the optimal decision-making efficiency of the supply chain. Eventually, the influence of some parameters in the model on the profits of supply chain players is analyzed by numerical examples.