The histology and histochemistry of ovaries in sexually matured female mandarinfish. Siniperca chuatsi. in Bao'an Lake, were studied. The development of oocytes of mandarinfish underwent five consequent phases. Atresia existed all year, which divided iiito prespawning atresia and post-spawning degeneration. In the annual cycle, the ovaries were resting stage (stage I) from November to March next year. and prematuration ovaries (stage IV) in April. Reproductive season of mandarinfish was from late April to late June, and spawning ovaries (stage V), first post-spawning ovaries (stage VI-IV) ancl second spawning (stage V) were found in this period. In July, most ovaries were in second post-spawning (stage VI-IV) which were gradually degenerated and reabsorbed to stage I from August to October. In a yearly cycle, the ovaries of mandarinfish spawned twice, and the interval was 30-40 days. Yolk materials of oocytes in mandarinfish had three forms:yolk vesicles, oil droplets ancl yolk granules. Polysaccharides were abundant in yolk vesicles. Oil droplets mainly contained lipids, and yolk granules were composed of proteins, lipids and polysaccharides.