Abstract: Service principal plays an important role in agricultural social service system. The key issue of sustainable development of agricultural social service is whether service provided by service principal can be accepted continually by farmers. On the base of game theory, the article analyzes the process of game between service principal and farmers and finds that service quality and cost-benefit of service principal are important factors that impacting on service sustainable development. Sustainable and stable development of agricultural social service can’t be achieved without excellent service and participation of farmers. Only service that adapt to market demand and bring benefit to farmers can be accepted.