The effect of science popularization activities is the result of common effort in knowledge chain of science popularization creation and dissemination. Science popularization team plays a core role in the realization of science popularization resource sharing. Under the condition of moral hazard, short-term cooperation models can’t effectively motivate project leader to work together. Based on principal-agent theory, this paper designs long-term cooperation models of science popularization project under the condition of repeated game and proposes to establish expert database and reputation archives of science popularization workers for objective evaluating ability of science popularization workers. Through the analysis of the mathematical model, the author thinks that the reservation utility of project leader should be no less than the sum of discounted reservation utility of short-term cooperation mode by science popularization capacity and the expected revenue loss. The long-term cooperation mode achieves win-win results by balancing the profit between the parties and provides theoretical basis and advices for science popularization activities of exploration and innovation.