It’s difficult or impossible to understand party newspaper without the party. The various phenomenon occurred in the Yan’an Period were closely related to the evolution and maturation of the Chinese Communist Party (CCP), which is a typical Leninist Party. This central premise requires the researchers to expand the problematic domain restricted by the media-centralism, taking into consideration of the party politics. Only then can we get a better understanding of the journalism within a wider historical background and a more diversified context. The CCP perfected the theory and practice of the mass line in the Yan’an Period, achieving an important breakthrough to the organizational mode of the Leninist Party. The party newspaper played a key role in the practice of the mass line. In the meanwhile, the logic of news production had been reconstructed by the principles of the mass line. Following the clue of transformation of the party politics, this paper attempts to make a preliminary analysis on the mechanism of the journalistic mass line in the Yan’an Period.