The activity of the great ocean conveyor,i.e. the thermohaline circulation, and its link to climate variability, is a new problem noticed by international scientific community since the late of 1990s.The objective of this paper is to provide a summary of the conveyor' s operation in global climate system.Both the conceptual diagram depicting the conveyor belt and the important role of it in the climate system have been addressed. Our current research status, together with the future research emphases designated by international scientific plans, is summarized. Emphasis has been put on the revelation of the role of the thermohaline circulation in global climate system.