Abstract: In order to ensure the annual gas demand of farmers in North China and explore the gas characteristics in the household biogas digester with constant temperature, the 3 m³ solar constant temperature biogas digester was developed. Stability of the biogas, biogas characteristics under different fermentation temperature and different fermenting materials, annual biogas characteristics, and operation strategy were studied with this system. The batch type experimental research showed that the system could be run steadily and continuously throughout the year. And the annual cumulative production of biogas was 398.52 m³ under the weather conditions in Lanzhou area. The system could realize constant temperature anaerobic fermentation at 26, 28 and 37 ℃ when the lowest ambient temperature exceeded -19.9, 0.7 and 6.9 ℃, respectively. In addition, the methane volume fraction was improved prominently or the production gas cycle was shortened when the pig manure was mixed with corn straw, wormwood and lotus leaves by a certain mixing proportion. Compared with pig manure fermentation, the volume fraction of methane of biogas produced by mixed material was promoted by about 8% as the volume ratio of raw material pig manure ∶ wormwood ∶ water ∶ inoculums was 1∶2∶2∶1. It could shorten the fermentation period remarkably when the wormwood, lotus and pig mature were taken as fermentation materials. At the end of the fermentation process with the mixed material at 37 ℃, the daily biogas production was difficult to meet consumers′ demand. And the daily average biogas production could keep 0.8 m³ in a week if we supplied 0.025 m³ new material with the same proportion. This experiment can provide reference for the efficient use of renewable energy. Utilizing the mixed materials can regulate the gas production and gas quality, and advices can be adopted for users to use raw materials which come from local resources according to season conditions. Three pails of new materials with same proportion(0.025 m³) are needed to replenish for anaerobic fermentation equipment every week, when the stability of gas production is unsure and the daily gas production is hard to satisfy users requirement that is to keep the daily gas production of 0.8 m³ one week. When the gas consumption increases, the measures that regulate temperature and feed to add the gas production can be adopted to satisfy the biogas utilization demand. The biogas production system with constant temperature operates steadily all the year round. Meanwhile, biogas can completely satisfy the demand of 3-5 people′s household cooking and gas in a year. And the biogas digester using pig manure as raw materials can still achieve the gas production with(26±1.5) ℃ constant temperature and the daily biogas production of over 1.3 m³, when the average environmental temperature range is between -23.8 and -5 ℃ in winter, even encountering 3 successive overcast or snowy weather. The biogas digester using pig manure and wormwood as raw materials can achieve the 37℃ gas production and the daily biogas production of over 1.7 m³. And when the year-round solar radiation range is 11.7-17.4 MJ/m², the fermentation tank per cubic meter needs 10 glass vacuum tube solar collectors of φ58 mm×1 800 mm.