Abstract: Seven isozymes in eight different tissues of Pinctada martensii were analysed by level slab polyacrytamide gel electrophoresis. The results showed that there were not A- GPDH and ADH isozymes in the any of eight tissues. The expression of LDH isozymes had one faint band only found in liver. The isozymic phenotypes of ME、MDH and SOD had evident difference among certain tissues, but the EST isozymes exhibited an apparent tissue-specif icity.