Abstract: Because there is no profit incentive, the organizations for gratuitous services are generally considered having serious incentive difficulty, but most of which have the same efficiency as for-profit-enterprises. This implied that, except profits, many other incentive mechanisms are also important. "Output benchmark" and "self-incentive" are main incentives in the organizations for gratuitous services. The paper analyzes these two incentive mechanisms using principal-agent model and indicates that "the long term benefit" and "altruism" can produce strong incentive to the agents, but the existence of the uncertainty weakens their incentive effects.