The vertical slab polyacryanmide gel ectrophoresis technology was used to study the EST and MDH of Aleuroglyphus ovatus and the EST of Tyrophagus Putrescentiae at different stages. The result indicates that the same and the different characters is existed in the isozyme of the acari at different stages, and it is feasible to classify the different species by the isozyme bands of the larva and nymphae.