Abstract: Marx's “German Ideology” is another  work of significant importance after the publication of “The Economic and Philosophic Manuscripts of 1844”. If the latter is a promise of Marx's philosophy，the former is a specific show of the doctrine of existence. The achievement of “German Ideology” indicates that according to his own ontological principle Marx brought us into a living world and worked out a new principle for us to understand and reform the world by revealing the secrets of man's existence. Therefore,Marx's theory of communism means the truth of man's existence.

Key words: Brightening, man, existence, German Ideology