This paper describes the coal petrological characteristics and the action and significance of low organism during the high sulfur coal formation in the Wuda coalfield, Inner Mongolia, Northern China. Petrological and geochemical studies show that No.9 coal seam, formed in tidal delta plain setting, not only have a high content of desomocollinite (up to 64.7%) that indicates a strong gelafication and bacteria activity during coal accumulation, but also have the highest sulfur content (3.46%) because of seawater influences. The values of both organic and pyritic sulfur isotopes (from -12.3* to 5.8* and from -18.7* to 1.1* respectively) in Wuda coals are more variable and generally tend to be more negative in high-sulfur coals, which indicates the heavy microbiological isotopic fractionation and a large portion of sulfur in high-sulfur coals originating from bacteriogenic sulfide. Findings of pyrilized rod-like bacteria, cyanophyte’s gelationoous sheath and degraded algae organic matter suggest that bacteria and algae play an important role in the formation of the high-sulfur coal. The characteristics of spectra, Fe+ and its associated inorganic elements ions of the No.9 coal seam were studied by using the high-resolution Time of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). Besides Fe+ ( 54Fe+, 56Fe+, 57Fe+ ), other associated inorganic ions, such as 27Al+, 28Si+, 29Si+, 30Si+, 40Ca+, 63Cu+, 65Cu+, 64Zn+, 66Zn+, 67Zn+, 68Zn+, 58Ni+, 60Ni+, and 62Ni+ were detected. The results show that the bacteria play an important role in the medium change, migration and activation and enrichment of Cu and Zn in the formation of pyrilized rod-like bacteria. Petrological and geochemical studies show that No. 9 coal seam, formed in tidal delta plain setting , not only have a high content of desomocollinite (up to 64.7%) that indicates a strong gelafication and bacteria activity during coal accumulation, but also the highest sulfur content (3.46%) because of of seawater influences. The values ​​of both organic and pyritic sulfur isotopes (from -12.3 * to 5.8 * and from -18.7 * to 1.1 * respectively) in Wuda coals are more variable and generally tend to be more negative in high-sulfur coals, which indicates the heavy microbiological isotopic fractionation and a large portion of sulfur in high-sulfur coals originating from bacteriogenic sulfide. Findings of pyrilized rod-like bacteria, cyanophyte’s gelationoous sheath and degraded algae organic matter s uggest that bacteria and algae play an important role in the formation of the high-sulfur coal. The characteristics of spectra, Fe + and its associated inorganic elements ions of the No. 9 coal seam were studied by using the high-resolution Time of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). Besides Fe + (54Fe +, 56Fe +, 57Fe +), other associated inorganic ions such as 27Al +, 28Si +, 29Si +, 30Si +, 40Ca +, 63Cu +, 65Cu +, 64Zn +, 66Zn +, 67Zn +, 68Zn +, 58Ni + The results show that the bacteria play an important role in the medium change, migration and activation and enrichment of Cu and Zn in the formation of pyrilized rod-like bacteria.