Abstract: The morphology and isozyme of six geographical rotifer (Brachionus plicatilis) strains were examined and the relationship among the rotifer strains were compared by morphometry and isozyme eletrophoresis, combined with life history. The results showed that different rotifer strains had significant difference in morphology and obviously differentiation in isozymes. The cluster analysis of morphology and isozyme indicated that there was a close relation- ship between Neimeng and Xizang rotifer strains and among Liaoning, Dalian, Tianjin and Sandong rotifer strains. The cluster analysis of the life history revealed that the life history characters were not suitable in similar studies.