We use Sperber's intermediairies and the firm theory to analyze the rural socialized service organizations. By studying the case of the melon association in Beihe Village of Uqiao Township in Beijing, we find that the basic existing objective of this association is to save transaction cost. The theoretical research and case analysis results show that the dispersed peasants are unable to solve the contradiction between small-scale production and large-scale market. However, the rural socialized service organizations, the purpose of which is to serve the benefit of the peasants, can save the transaction cost of peasants and safeguard the economic interests of the peasants.