Abstract: A zooplankton seasonal variation investigation was made in Yangshan Port channel. Zooplankton density was the highest in summer. Spring biological density was fall slightly higher. There were 6 dominant species in result. One of the species Limnoithona tetraspina was the dominant species throughout the year. And it was the most obvious in winter(Y=0.48), the least obvious in summer(Y=0.04). The Acartia clausi was the dominant species in spring, autumn and winter. The Acartia pacifica was the dominant species in summer and autumn. The Paracalanus aculeatus was the dominant species in summer, autumn and winter. The Sabellaria was the only dominant species in spring. And the Paracalanus parvus was the only dominant species in autumn. However, the Labibocera euchaeta was not the dominant species anymore. So Yangshan Port was affected by human.