Abstract: The downfall of the Ming Dynasty is not only the breakout of economic and political crisis in traditional Chinese society,but also the result of moral crisis.With a historical consciousness,Gu Yanwu deeply reflected the lessons from the downfall of the Ming Dynasty and devoted himself to exploring the way to reconstruct Chinese moral civilization.His moral and ethics ideology has three important features:1).He criticized the traditional negative nationality in  a comprehensive way for the first time.2).He proposed a moral limit.3).He a advocated the freedom of personality.All these are the modern factors in Gu Yanwu’s ethics and moral ideology,and they are the signs of traditional Chinese ethics to transit into a realistic one.

Key words: Gu yanwu, ethics, moral limit, rationalization, modern transition