The early relationship between the Chinese Communist Party (CCP) and the Kuomintang (KMT) is regarded as an important issue in contemporary Chinese history, but the explanation of this phenomenon has differed for a long time. There is a major dispute in controversy in interpretations of this event. Some hold that the KMT "accommodated Communists," and the CCP insists that the Communists "allied with the KMT," The CCP realized that allying with the KMT was the correct choice at the time, and it was also in accordance with the Marxist-Leninist revolution strategy. Why dose the CCP say so? And what is the truth? This essay, from the perspective of the history of the Chinese Communist movement, attempts to understand what the CCP means by the "historical conditions of the time?" Why was cooperation with the KMT the right historical choice? Is it possible or not to say, from the point of view of the CCP, that joining the KMT was "the only choice?" In the 1920's, both parties were facing the difficulties of social mobilization, and there also existed the complementary interaction for revolutionary identification. In fact, the CCP leaders of that time clearly recognized that the only method which Dr. Sun Yet-sen would accept was that Communists could join the KMT as individuals, instead of as a group under the name of the CCP. On the other hand, because the Comintern was supporting both the CCP and the KMT, if the CCP did not join the KMT, the Comintern might have had to choose between the two parties. Since the danger of losing the support of the Comintern was much greater than that of joining the KMT, we may say that for the CCP, joining the KMT was in fact the one and only choice they had at the time.