A batch anaerobic test was conducted to examine the biodegradation of 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,6-dinitrophenol through measuring accumulative methane production. The Relative activity values were used to judge the inhibition level of nitrophenols on methanogenic bacteria. The test conditions was as follow: glucose was used as co-substrate and the temperature is 35 degrees C. It didn't cause inhibition when concentrations of 2-nitrophenol, 4-nitrophenol, 2,6-dinitrophenol and 2,4-dinitrophenol were below 24mg/L, 20mg/L, 12mg/L and 4mg/L respectively. Slight inhibition was caused when concentrations of 4-nitrophenol and 2,6-dinitrophenol were 24mg/L and 16mg/L-24mg/L respectively. Middle inhibition when concentrations of 2,4-dinitrophenol were 8mg/L-24mg/L was observed. The inhibition level was 2,4-dinitrophenol > 2,6-dinitrophenol > 4-nitrophenol > 2-nitrophenol.