This article gives a concise description of the researches and practices of knowledge management,and then finds the obvious trends that explicit knowledge is prone to be emphasized and tacit knowledge be underes-timated.Such phenomenon doesn't match the key role tacit knowledge played in the knowledge management.By clarifying the knowledge and defining the notion of tacit knowledge,the author elaborates tacit knowledge and holds that the tasks and objectives of tacit knowledge management mainly include recognition,exploitation,retain-ing and innovation of tacit knowledge.