Abstract: Xiphinema diversicaudatum and Longidorus elongatus are economically important plant-parasitic nematodes as virus vectors.Both of them are on the lists of quarantine pests related to the import plants in China.Molecular methods and genetic analyses based on the DNA sequences of nuclear ribosomal DNA ITS were conducted to determine the longidorids species and phylogenetic relationships within 6 taxa 15 populations,including X.diversicaudatum,X.brevicollum,X.insigne,L.elongatus,L.intermedius as well as Paralongidorus maximus.Seven DNA sequences varied from 1400bp to 2100bp for 7 targeted samples collected from Netherlands and Yunnan,China,respectively,both homology tree and phylogenetic tree were set up using MEGA4.0 software.Among them,X.diversicaudatum has 55% similarity with the other 4 studied Longidorids nematodes.Similarly,there is 56% genetic divergence between L.elongatus and 3 other studied Longidorids.The genetic variation of the studied nematodes had ranged from 10% among X.diversicaudatum to zero among L.elongatus.