Abstract: Resistance of 30 free pollinating families in the second-generation seed orchard for Pinus massoniana were studied by artificial inoculation with Bursaphelenchus xylophilus(Pine wood nematode)under natural conditions.The genetic variation pattern of resistance to pine wilt disease was analyzed based on mortality rate,and resistant families were selected.The results show that after inoculation with B.xylophilus,the mortality rates of families differed significantly,with the genetic variation coefficient of interfamily mortality of 37.03%,and broad-sense heritability was 0.6323,confirming that the resistance to pine wilt disease at the family level was controlled strongly by gene.Nine families were selected based on the standard of resistance genetic gain no less than 20%,and a 29.62% resistance genetic gain was obtained.Among them,family No.59 has the strongest resistance,with a mortality rate of 5.79%,14.48 percentage points lower than the population mean,and the genetic gain of resistance reached 45.17%.