With the advantages of contacting people from all walks of life，the mass organizations undertake the mission of the Party’s mass work，they coordinate to promote the central tasks of the Party and the government. Taking the China Association for Science and Technology as a case，this paper analyzes its organizational mission by studying its founding and development process and its responsibilities and tasks，explore the implementation action of its organizational mission and then propose that the mass organization should strengthen its consciousness of mission，promote its duties responsibility，and coordinate the implementation action of the Party and government.