Two types of rDNA-ITS(Type A,900 bp and Type B,1 100 bp) were demonstrated to exist in Ditylenchus destructor populations on sweet potato in China.The D2/D3 regions of 28S rDNA from 22 populations of D.destructor were amplified with universal primer pairs D2A and D3B.All 22 populations yielded one single fragment about 780 bp.Sequence analysis and alignment were conducted by using the software MEGA4 and DNAMAN5.2 and all 22 sequences were submitted at the GenBank.The results showed that sequence differences of D2/D3 region were only in a few sites,and that the similarity was 97.2%.Two types could be distinguished in the phylogenetic tree by using UPGMA method.The evolutionary relationship between two types and the origin of Ditylenchus species were discussed.