Now,the U.S. capital market is the best one on the fracts of market levels,market structure and the operation mode.OTC market as the most important constituent part,which play a key role in the capital development and expansion. Thus,this article introduces the whole condition of OTC systermaticaly,integrating the development,current situation,hierarchical structure as well as supervision mechanism. And this paper provides the suggestions to perfect China's OTC market,which based on China's capital market situation and the reference to U.S.. <<