Abstract: The “Third Period Theory”,formed in the Sixth Congress of the Communist International,held that the overall capitalist crisis after World War I had come,and with the revolutionary climax of worldwide labor movement as well as national liberation movement,it was time to realize world revolution.Influenced by this theory,the Communist Party of Taiwan had made serious leftist mistakes,causing crazy repression of Japanese colonists and its destruction,for which,the Communist International,the theory maker and guider,should be responsible.

Key words: the Communist International, the Third Period Theory；the Communist Party of Taiwan；Leftist Mistakes