Aiming at the problem of product supply chain realized Extended Producer Responsibility (EPR) based on third party recovery, the principal-agent relations among subjects were analyzed, and a principal-agent incentive contract model for manufacturer to enforce the EPR was built. Under symmetric and asymmetric information of contractors, the optimal incentive pay of manufacturer and the optimal efforts of seller with reclaiming agent were determined by this model. Meanwhile the optimal contract mode between principal and agent was suggested. Cost saving of agents' hidden activities and its effect on principal's revenue were discussed, and the suggestion for product supply chain to realize EPR was proposed from the perspectives of institutions, market and technology was advanced.