Abstract: Lenin's thoughts about the mass line of the proletarian party are the fundamental views and ideas about "why should adhere to the mass line and how to adhere to the mass line?" Which were formed when he was leading Soviet socialist revolution and construction. The thoughts include the significance of the mass line for the proletariat political party, target selection of the proletarian party adhering to the mass line and the method or path of proletarian party adhering to the mass line. The paper conducts a study of Lenin's ideas to provide for the Communist Party of China the practical experience, the theoretical foundation as well as the realistic enlightenment in adhering to the mass line under new circumstances.