Collectivism is the fundamental law of the socialist ethics. Basing upon Chinas social reality after the establishment of the Republic, and its special social structure, this paper examines and analyzes how in history collectivism gradually comes into being, putting forward a new notion of unit collectivism. The paper posts, through the illustration of the relationship between the collectivist principle and the organizational attachment, the setting in which collectivism came into being before Chinas opening up to the outside world, and hopes to give a relatively reasonable explanation to the historical value and the realistic significance of the collectivist principle.