Abstract: Microbial degradation of coal is an effective way for efficient and clean utilization of low rank coal,and actinomycetes are one of the main microbes to degrade low rank coal.Photooxidation pretreatment of low rank coal can increase the oxygen content of low rank coal,which will help to improve the biodegradation rate of coal by microorganism.In order to obtain high-efficiency biodegradation strain of lignite,five actinomycetes and four photooxidized lignites were tested by actinomycete-coal matching experiments.After comparing the degradation effect of 5 kinds of actinomycetes and 4 kinds of photooxidation lignite,the dominant strain selected was Streptomyces viridosporous.Taking the absorbance value at 450 nm of the degradation solution obtained by Streptomyces viridosporous as the index,the single factor experiments were carried out to determine the technological condition of biodegradation of Inner Mongolia Shengli lignite by Streptomyces viridosporous. Finally,the determined optimum technological conditions were listed as follows: coal slurry mass concentration of 0.2 g/20 mL,inoculums size of 3.0 mL/20 mL,incubation time of 10 d,oscillation frequency of 160 r/min,coal particle size of 0.150-0.075 mm and incubation temperature of 28 ℃ .According to this condition,the degradation effects of Streptomyces viridosporous degrading GZTH,GHYH and GYBH were studied.The results show that under this condition,the degradation effects of Streptomyces viridosporous degrading the three lignites are all improved to some extent. It can be seen that the process conditions of photooxidation lignite degraded by Streptomyces viridosporous taking Shengli lignite in Inner Mongolia as the sample has a certain universality for the degradation process of different photooxidation lignite,which can be used as a reference for the study of the better process conditions for the degradation of photooxidation lignite by Streptomyces viridosporous.