It's commonly believed that global warming may possibly give serious impact on agriculture and forestry, ecosystems, human health, water resources, sea level and storm intensity in the future, although the scientific proof is incomplete and that there remain many uncertainties about the nature and direction of climate change. Attention has been focused on possible extremes of climate change and the need for better understanding of climate processes to improve the prediction which is needed for the governments to make more evidence-based policy decisions through comprehensive, systematic observation and prediction of the Earth system and climate change. Covering about 70% of the earth's surface, ocean plays a critical role in the global temperature, water and carbon cycle and controls climate. Exchanges of water, gases, heat and momentum are continually taking place across the atmospheric-ocean interface and ocean powers climate and regulates global temperature, CO2 and water contents in the air by acting as a giant heat and CO2 reservoir. Our understanding of the role of the ocean on the climate process is essential in predicting climate variability and change through successful implementation of Global Ocean Observing System.The impact of global climate change on the ocean and also the role the ocean in the climate change as well will be discussed more detail at the presentation. The strategy in building ocean observing system which is essential in the study of global climate change will be also discussed.