Based on monthly sea ice extent data from 1979 to 2006, the sesonal change and t endency of Antarctic and Arctic sea ice were statistically analyzed. The results show as follows: the seasonal change of Antarctic sea ice is more remarkable th an that of the Arctic. In recent 30 years, Arctic sea ice decreases rapidly, esp ecially in summer and autumn, and more quickly since the mid 1990s.The decline m ainly appears over the Arctic Ocean near the Pacific in summer and autumn, over north of the Pacific in winter and spring. Antarctic sea ice shows uptrend since the early 1980s, especially in summer and autumn. There is a decreasing centre near Antarctic Peninsula. In addition, there are two increasing centers over Ross Sea and south west of Indian Ocean. The centers move eastwards and go back around Antarctica w ith the seasonal transition from summer to spring.