Based on maximum parsimony phylogeny tree of ITS-nrDNA sequences of 121 isolates downloaded from GenBank, A phylogenetic tree was constructed by the MEGA4.0 package by Maximum parsimony method. Their phylogenetic relationships were studied. The present results showed that Phytophthora species were clustered into five groups. The analysis of ITS-nrDNA sequences didn’t support the idea that P.cryptogea and P.drechsleri are synonymous. The MP (Maximum parsimony) tree also showed that P. undulata and P. batemanensis was more homogenous with Fythium. The other Phytophthora species were also discussed in this paper.