Abstract: Abstract: In order to solve the problems of unstable gas production, the low biogas production rate, and the zero-gas production in winter existing in the traditional biogas digester with a brick-concrete structure, an over-ground household thermostatic biogas digester heated by solar energy was developed and constructed. The system consists of a glass evacuated tube collector with the collector area of 2.96 m2, a 2 m×2 m×3.2 m insulating chamber, a 3 m3 plastic biogas digester, a 3 m3 reservoir bag, an automatic temperature controller, a heating coil, and some other small parts. The energy collected by the solar collector is stored in water and the hot water is circulated in the heating coil by the circulating pump. The pump is directly controlled by the automatic temperature controller. The automatic temperature controller can be set an initial value. If the fermentation temperature is below the set point, the automatic control system will work to let the circulating pump start, and then the hot water will transfer heat to the biogas digester through the heating coil to keep the fermentation temperature at the set point. And similarly, the circulating pump will be shut down, controlled by the automatic control system, if the fermentation temperature reaches or exceeds the set value. Experimental study on the gas production of the system in winter was carried out. The fermentation material consisted of 0.5 m3 pig manure, 0.5 m3 inoculum, and 1 m3 water. During the experiment, the temperature data was recorded by the Agilent data acquisition instrument, the daily gas yield was measured by the gas meter, the gas content is measured by the portable gas analyzer, and the pH value was recorded by the portable pH meter, which was done at 17:00 every day. In order to ensure the uniformity of heat transfer and material liquid in the digester, stirring work was done daily. By analyzing the data collected, we could conclude that the solar collector can ensure the digester's stable operation at a constant temperature of (26±2)℃, with the ambient temperature ranging from -19.8 to -10.0℃ during the 39 days fermentation period. The cumulative gas production was 42.520 m3. When the system was operated steadily and the gas production rate was relatively smooth and steady, the average daily gas production was 1.380 m3. The average content of CH4 was 58.2%. And by also analyzing the temperature data of a typical day (The day after two cloudy days ), we could conclude that the lowest solar hot water temperature was higher than the fermentation temperature needed, which could ensure the continuous heat supply from the solar water to the digester, despite bad weather. It showed that the system has a good ability for resisting disturbance from its surroundings. According to the biogas engineering and technical specification of China and the average daily gas production, the system can satisfy 4-5 farmers' domestic gas demand in the winter days of cold areas. Therefore, the over-ground household solar heating biogas digester was of great significance to meet farmers' domestic gas demand, recycle organic waste resources in rural areas, and improve the residential environment as well as the construction of a new countryside.