Abstract: This paper introduces a new technology making a rural biogas plant of mesophilic fermentation, the key of which is a set of efficient installation recovering waste heat from a biogas—diesel engine. The system exhausts no extra cnergy and waste heat recovered from the engine can entirely make compensation for a heat loss of the biogas plant, whicn is an economic heating source for mesophilic fermentation. If spreas and use, this new technology would make great contri bution to yearlong steady efficient output of a rural biogas plant and make biogas a reliable energy resource in the countryside.