In order to clarify the seasonal composition and abundance of zooplankton community in Macheon Bay. the study was carried out trimonthly during the period from April 1996 to January 1997. 37 taxa and 7 unconfirmed species of zooplankton was identified. It consisted of 28 species of Protozoa. 1 species of Cnidaria, 1 species of Annelida, 2 larva of Mollusca, 3 species of Rotifera, 4 species and 4 larva of Arthropoda and 1 larva of Echinodermata, respectively. Seasonal succession of the dominant species was Tintinnopsis beroidea in the spring. Copepodite in the summer. Tintinnopsis directa in the autumn and Ceratium fusus in the winter. Abundance of zooplankton ranged from 4.720 to 4 1.215 inds./ . It was high in the summer (4 1.215 inds./ ) and low in the spring (4.720 inds./ 1 ). Dominant index ranged from 0.133 (in the spring) to O. 551 (in the winter). Species diversity index ranged from 1.114 (in the winter) to 1.996 (in the spring).