Abstract: A10 samples were collected from the Jurassic system of the Mazhuang gas reservoir in the Junggar Basin. Formed in a swamp- shallow shore depositional environment, they consist of rich TypeⅡ B and Ⅲ organic matter with R0 values less than 0.74% at the low evolutionary stage. This paper mainly discusses questions on the amount of anerobic fermenting bacteria, the type and distribution of methanogen, and the methane yield of per gram organic carbon in the process of the simulahng fermentation experiment and so on. The numbers of permenting bacteria are from 5×10²/g rock to 2.3×10⁴/g rock. At 35℃-65℃,Methanococcus is found in all samples, at 55℃, Methanobocterium is found in No. 7 sample. Simulating experiment results show: (1 )methane accumulation yields are the most at 35℃, from 29.48ml to 39.41 ml, over 80% in the total gas-producing yield. (2)in the gas product, methane is the major, secondly carbon dioxide, and only a trace of ethane and profane is present. (3)from the methane-producing yield of per gram organic carbon, it can be seen that most of samples produce 50ml/g org. to 200ml/g org. gas, and the highest reaches to 568ml/g org. gas. (4)the methaneproducing ability is different at different temperature, 35 ℃ 65 ℃ 55 ℃. (5 )under the condition of the same sample and temprature, with the increase of the methane yield the carbon dioxide yield is also increasing. (6)the δ¹³C values of methane are - 40.12‰, to - 43.98‰, at 35℃, - 56.82‰ to - 60.10‰, at 55℃, -58.06‰ to - 65.11‰, at 65℃, and the median value of the carbon isotopic ratio of methane at 35℃ to 55 ℃ is nearly similar to the δ¹³C value of methane from the Mazhuang natural gas reservoir.This poper provides some evidence for that methanogen and other anaerobic microbes still have activity beneath over 2000m sediments and also it gives many significant scientific information to the study on geomicrobiology and some of of natural gas-forming mechnism.