Nowadays,the low efficiency of the peasant collective action delays the pace of the new countryside construction of China . There is plenty of research which discusses the reasons causing this phenomenon and how to enhance the peasant collective action efficiency in academic circles . However,Cost-Benefit Analysis has been ignored more or less in the existing research on peasant collective action efficiency . As a result,it is hard to find a practical path of improving peasant collective action efficiency . According to the Cost-Benefit Analysis,currently the high cost of peasant collective action is the root of its low efficiency . Decreasing peasant collective action costs and improving its efficiency must rely on social capital accumulation in rural areas . According to the stages of peasant collective action,peasant collective action costs can be subdivided into mobilization costs in the mobilization stage,direct resource costs and incentive costs in the operation stage,and supervision costs in the maintenance stage .Among these stages,mobilization costs are generated from collective action organization construction .Direct resource costs include three aspects : target costs,participation costs,and coordination costs . Incentive costs are generated from the transmission costs of incentive messages|Supervision costs include three aspects : trust mechanism construction costs,constraint costs,and information transmission costs . Due to three inherent characters of the rural social capital,that is,rural social trusts,rural social rules and rural networks,rural social capital plays an important role in decreasing peasant collective action costs . Rural public services and peasant self-supply are typical peasant collective actions,the enhancement of which depends on the local social capital . During the rural public services and peasant self-supply,rural social capital can decrease the costs in the stages of mobilization,supply and supervision . Furthermore,by reducing the costs of mobilization,direct resource,incentive and supervision,the total costs of rural public services and peasant self-supply will be cut down and the efficiency will be increased . Affluent social capital is conserved and accumulated in F village in Tongcheng City,Anhui Province . The social trust of honesty and integrity,the social rules of loyalty,consideration,benevolence and righteousness,and the widespread social networks in F village played important roles in decreasing peasant collective action cost and improving road construction efficiency . Specifically,firstly,during the road self-construction launching stage,social capital in F village decreased road self-construction mobilization costs .Secondly,in the road self-construction operation stage,social capital in F village decreased direct resource costs and incentive costs . Thirdly,in the road self-construction maintenance stage,social capital in F village decreased the supervision costs .Practices in F village have proved that social capital in rural areas plays an important role in decreasing peasant collective action costs and improving peasant collective action efficiency .