Abstract: China’s economy has shifted from rapid growth to high-quality development. Corporate social responsibility has received widespread attention, and the media has also flourished as a vehicle for social responsibility disclosure. The effects of internal and external governance of enterprises in different cities are different, the degree of media concern is different, and the performance of corporate social responsibility is also completely different. Based on this, this article uses 2010-2018 listed company social responsibility data and city data to empirically test the impact of media concern on corporate social responsibility, and further study the interaction between media concern and city size. Research shows that negative media reports, especially deep negative reports, can promote the improvement of corporate social responsibility, and media concern can be an effective means of monitoring and restricting corporate behavior. The analysis of heterogeneity found that the supervisory role of media concern is more obvious in eastern enterprises, large enterprises, high-efficiency enterprises, and it is mainly concentrated in technology-intensive industries and public service industries. Further analysis verifies the negative moderating effect of city size in it. There is a substitution effect between it and media concern. Compared with large cities, small and medium-sized cities have more significant improvements in corporate behavior when they receive negative media coverage. This feature is particularly evident in the central and western regions.