For an anaerobic fermentation system, the temperature is one of key factors which affect the efficiency of biogas production. A parabolic trough concentrator (PTC) was used as the heat source for an 8m3 underground anaerobic digester. To improve the efficiency of concentrating solar collectors and the biogas productivity of traditional anaerobic fermentation system, the sizes of important components in the digester were determined, and the energy balance was also calculated. Moreover, the angle change of solar concentrator in Yangling was counted, the angle of the collector during one year was optimized, and the inclination angle and installation method of the concentrator bracket were also designed. It was found that feed heat loss (16077.31kJ/d) and wall heat loss (23180.01kJ/d) were the two main heat loads in this system. The key parameters of PTC were determined: the size of aperture was 2.4m, the focal distance was 0.6m, the area of collector was 4.16m2, and the diameter of collector pipe was 0.0168m. In addition, the heat transfer of anaerobic reactor was simulated through Fluent software. The simulation results revealed that interior temperature in the digester could be maintained at 35℃. A PTCbased anaerobic digester with similar parameters of simulation model was designed to verify the simulation effect. The experiment results indicated that the temperature range of material liquid in the reactor could be kept at 33.6~35.8℃, approximately consistent with the Fluent simulation. The results in this study provide a new solution for efficient and lowcost biogas fermentation device.