Abstract: Thermal loss is a bottleneck problem that restricts the development of biogas engineering in the cold areas of the north. A comprehensive and systematic analysis of biogas project annual thermal loss and exploring its distribution rule is the basis and premise of realizing the energy conservation and consumption of biogas projects. It is also the basis for the comprehensively and scientifically evaluating the reasonable and effective energy use for the biogas engineering heating system and improving the utilization rate of energy. The thermal energy loss of biogas projects mainly includes the heat consumption required for the temperature rise of the newly invested fermentation raw materials and the heat transfer heat consumption of anaerobic fermentation reactor. This paper establishes a monthly calculation model for thermal energy loss of biogas projects, and applies it to a middle temperature anaerobic fermentation biogas project in Harbin City, Heilongjiang Province, and obtains the thermal energy loss of the biogas project in each month. The results show that heat transfer heat consumption of the anaerobic fermentation reactor envelope structure accounts for 70% to 90% of the total heat consumption in the total heat loss of the anaerobic fermentation reactor, the key to energy saving of anaerobic fermentation reactors is the energy conservation of the envelope structure. Reducing the body shape coefficient of the reactor and increasing the thermal resistance of the envelope structure can effectively reduce the energy consumption of the anaerobic fermentation reactor. In the total heat loss of biogas projects in each month, the energy consumption of fermentation raw materials accounts for 85% to 95% of the total energy consumption of biogas projects, it is a weak link in the energy consumption of the heating system for biogas projects, so recover waste heat from biogas slurry is an effective way to achieve energy conservation and consumption reduction of biogas projects. The loss of thermal energy in biogas projects accounts for 15% to 37% of the energy production through a comparative analysis of the monthly production capacity of biogas projects and the total heat loss. In the case of normal anaerobic fermentation, the energy production of biogas projects is far greater than the loss of thermal energy. Therefore, it is possible to achieve the output of biogas engineering in the cold regions of the north. The results of this study can provide a reference for the future comprehensive scientific and rational evaluation of the energy status of the biogas projects, reducing loss and waste in the process of energy use, and achieving low energy consumption and high productivity of biogas projects.