Twenty eight root-knot nematode populations on Psidium guajava were collected from Hainan Province. Based on morphology, isozyme and mtDNA, 25 populations were identified as Meloidogyne zhanjiangertsis ,2 populations as M. panyuertsis and 1 population as M. incognita. It was showed that M. zhanjiangensis was the predominant species. The technology and methods of identification on root-knot nematode were discussed in the paper.