Abstract: The thought of sufficient reason can be traced back to ancient Greece.At the beginning of the 18th century and on the basis of researches made by the predecessors,Leibniz formally and on the basis of researches made by the predecssors, Leibniz formally advanced the principle of sufficient reason.The principle was presented in the 3 aspects of the reasons to exist,to live and the know.And the thought exerts far-reaching influence on occidental philosophy.

Key words: principle of sufficient reason, principle of contradiction, traditional logic, law of logic, law of sufficient reason, Leibniz