The quantity of methane and the efficiency of COD have been used to study the anaerobic biodegradability of organic phosphorous pesticide(methyl chloride)wastewater,and the influence of pH and chlorine ion content to biodegradability are discussed.Experimental results show that:methyl chlorides wastewater has poor anaerobic biodegradability;Chlorine ion content has a lot influence on the biodegradability.When influent COD is 1 111.1 mg/L,chlorine ion content can reach 10.88 g/L,fundamentally there is no anaerobic biodegradability; the wastewater anaerobic biodegradability is improved under alkalecent condition(pH 8.0).