This paper illustrates the general experiment principle of anaerobic biological cotton pulp black liquor microbial degradation, including the process and result of experiment. The result shows that the decrement of COD may arrive at 80% by the strengthen effect of Photosynthetic Bacteria. The biochemical methane Potential (BMP) and Chemical Oxygen Demand (COD) of cotton pulp black liquor are also measured during the experiment using improved measure method. The equivalent of COD and BMP is verified as a result. Finally analysis is done based on the experiment result.