Since the 18th National Congress of the Communist Party of China (CPC), General Secretary Xi Jinping has emphasized in a number of meetings that “national data security must be guaranteed in an effective manner”. With the proliferation of data volumes and the increasing frequency of cross-border data flows, strong data security protection and flow regulation will become an important guarantee of national security. Hainan Province has persistently and thoroughly studied and implemented the spirit of General Secretary Xi Jinping’s important exposition on national data security, and comprehensively coordinated and promoted data security work in various fields. Sanya city has responded positively to national policy and regulatory requirements, stating clearly that in the future the City will pay more attention to “safeguarding national data security and strengthening protection of personal information”. Starting from security prevention and control of cross-border flow of personal data, the article not only analyzes deficiencies in the security prevention and control of cross-border flow of personal data in Sanya City but also puts forward four suggestions to improve security prevention and control measures of cross-border flow of personal data in Sanya City, taking into account experiences and practices of Shanghai and Guangzhou Municipality.