Abstract: Fumigation with methyl bromide(CH3Br) is a major method to treat the wood infested by the pine wood nematode(PWN)(Bursaphelenchus xylophilus) at present.The important factors,such as temperature,dosage,duration of fumigation,the wood size,moisture of the wood,size of the wood stack,and the position of the wood in stack,wrer analyzed respectively.The effect of fumigation was retarded by low temperature and improved by the increase of dosage.The duration of 72 h fumigation was proper.The worse result was obtained while the wood moisture was higher.The fumigation effect of the stack in bottom was the best.The sizes between 50 to 70m3 was suitable for fumigation.The impor tant factors affecting the results were temperature,dosage and duration of fumigation.The good results were achieved by increasing dosage and shortening duration of fumigation or prolonging the duration of fumigation and reducing dosage.The mortalities of PWN and Monochamus alternatus were l00% under CT value of 5 000～6000 at 4～10℃.