Abstract: The ultrastructure of liver was examined in Siniperca chuatsi Basilewsky at breeding season and non breeding season in their life cycles, with transmission electron microscopy. The hepatocytes contained an oval nucleus. Pronounced nucleoli were observed in each nucleus. Rough endoplasmic reticulum, mitochondria, glycogen and lipid droplets were abundant in cytoplasm of hepatocytes. The bile cannaliculi was makeup by rosettes of up to three hepatocytes. Hepatic sinusoid was formed by endothelial cells.Fat storing cell, Kupffer cell and fibroblasts were also present in the tissue of liver. The lumen of the bile cannaliculi and the space of Disse were occluded by many microvilli extended by hepatocytes. The shape of hepatocytes showed distinct changes before and after spawning, and nucleolus's activity also appeared obvious different. Nucleolar margination in hepatocyte was very rare before spawning, After spawning, nucleolar margination was very obvious and some of nucleolus appeared vesicles; an apparent decrease in the number of glycogen reserves in the hepatocytic cytoplasm, and some of hepatocyte had two nucleus after spawing. In prespawning adults, mitochondria in cytoplasm was abundant as rough endoplasmic reticulum, showing the marked glycogen reserves and the lipid accumulation in the fish. In non breeding season, most of hepatocytes contained two nucleolus, and an apparent increase in the number of lysosome was also found in the hepatocytes.