Abstract: MOOC has impacted the service mode of traditional library with a brand new education idea, and brought more possibilities for the future development of public library. Both domestic and foreign libraries actively participated in it. Taking the public class service in National Library of China as an example, this paper comprehensively demonstrated all aspects from the content construction, platform framework, display service, publicity and promotion of "National Library of China's Public Class Project". Using the questionnaire method, it collected and made researches of the user's habits and feedback, made deep thinking about the service contents, service channels and service effectiveness of public class in the future.