Effect of environmental factors on oxidation activity of added methane in Huangsong paddy soil developed from fluvo aquic matrix was studied.The results indicated that there existed two methane oxidizing systems found in soil,an aerobic methane oxidizing system (AMOS),and an anaerobic methane oxidizing system(AAMOS).The maximal activity of methane oxidation of AMOS was higher than that of AAMOS.Under aerobic condition,the methane oxidizing activity of AMOS was affected mainly by the contents of oxygen,water,methane and pH,temperature in soil.The methane oxidizing activity of AAMOS,however,was mainly affected by the contents of oxygen,methane,water and also by pH,temperature in soil under anaerobic condition.Oxygen inhibited the activity of methane oxidation of methane oxidizing bacteria of AAMOS.The optimum temperature for methane oxidizing activity lied from 25 to 35.After incubation at 50 for over 6 hours the tested paddy soil was unable to restore the oxidation activity of added methane when incubated again at 28,indicating that oxidation activity of added methane was completed lost.The optimum pH ranged from 6 to 7 for methane oxidizing activity.