Temperature is the critical factor affecting biogas production rate. Anaerobic digester is the heating object in biogas engineering, the heat load of fermentation tank is the basis of biogas project design and selection of heating system, which is related to the stability of anaerobic digest system and economy of heating system. Therefore, it is vital to define the heat load characteristics of the fermentation tank. The average temperature of the fermentation tank was calculated, and then the digester’s heating load was figured out, the maximum value was regarded as the system’s thermal load. This method was simple, however, which made the result deviated practical situation greatly. To accurately calculate the heat load of the fermentation tank, it was advantageous to match the heating system with the fermentation tank, and explore the optimal system configuration and operation strategy of the heating system in order to reduce the energy consumption and cost. The hourly meteorological parameters of special meteorological data set for analysis of thermal environment of building in China in the Shanghai area was used, based on the analysis of physical and mathematical model of fermentation of biogas project, the hourly accumulation of fermentation pool enclosure structure heat dissipation was calculated, and annual dynamic changes of fermentation pool heat load was obtained, which can be used to guide the design of heating system of fermentation tank. The essence of this method was to make steady algorithm time step shortened from a month to 1h, which enhanced the calculation precision obviously. Results showed that under the three different conditions, the relative errors of heat load model and experimental measurement were -5.98%, 3.93% and 5.39%, respectively. Thus, dynamic heat load model was of high precision, and it was acceptable to be applied to guide engineering design and operation, avoid the long time operation of the system under partial load, which had theoretical significance and reference value for the design and operation of biogas engineering.