Abstract: Otolith is a typical biomaterial which is composed of calcium carbonate and organic matrix. In order to study the micro-morphology of otolith，SEM observation was taken under different water conditions and of several treatment method otoliths. The otolith samples included fresh otoliths，alkali treated otoliths，Na₂EDTA treated otolith，and sliced otoliths under alkali and Na₂EDTA  treatment. The result shows the lapillus is composed of  hexagon or sham-hexagon aragonite which formed sheet or cylindrical structure,  while asteriscus is composed of ball or bean-shaped vaterite crystal. The polished otolith which was dealt with NaOH and Na₂EDTA can be distinguished as the crystal structure. The width of the daily increment is 2 μm～3 μm. The crystal structure of otoliths in different conditions show little difference，and as could be preliminarily inferred，the element content in water makes little effects on the crystal structure of otolith.