By analyzing the evolution of China’s opening-up policy after the reform and opening up, we revealed the spatial layout and opening-up goals of different stages, as well as the leading position of coastal cities in China’s reform and opening up. On this basis, a comprehensive index evaluation method was used to construct indicators in the fields of economy, society, science and technology, and policy to measure the opening-up level of 22 major coastal cities in China from 2008 to 2020. The results showed that since 2008, the overall opening-up level of all 22 major coastal cities has generally shown a fluctuating upward trend, hugely contributing to improving the overall level of China’s opening-up. Among them, Shanghai is located in the first echelon of opening-up, Shenzhen, Guangzhou, and Tianjin are in the second echelon, Ningbo, Qingdao, Xiamen, Dalian, Fuzhou, and Zhuhai are in the third echelon, and other research cities are in the fourth echelon. The opening-up level of China’s major coastal cities has characteristics in the four fields of economy, society, science and technology, and policy. In addition to the overall downward trend of the economic opening-up due to domestic economic structural adjustment and international conditions, the opening level in society, science and technology, and policy has steadily advanced. Furthermore, the analysis demonstrated a significant heterogeneity in the opening level among different coastal regions and cities within different regions.
