Winning the battle to defend the blue sky is a major decision and deployment made by the 19th National Congress of the Communist Party of China. It is related to meeting the people's growing needs for a better life, building a well-off society in an all-round way, and related to high-quality economic development and the construction of a beautiful China. In order to speed up the improvement of ambient air quality and win the battle to defend the blue sky, this action plan has been formulated.