Integrating openness and security is an inevitable requirement for weaving a tight financial safety net and perfecting a modern financial system with Chinese characteristics in the new era. The Report to the 20th National Congress of the Communist Party of China emphasizes that "we must resolutely pursue a holistic approach to national security". As a key component of national security, financial security plays a crucial role in ensuring socioeconomic stability and high-quality development. Although financial openness is not the root cause of financial risks, the relaxation of market access conditions and expansion of foreign financial institutions' business scope may facilitate cross-border transmission of external risks through channels such as global risk aversion and risk premium fluctuations, thereby threatening the security and stability of the financial system. In the policy design to ensure financial security, it is necessary to design an adjustment mechanism that takes into account both short-term external risk resistance and the sustainable development of long-term financial security based on the impact of external risk factors on financial security. The relevant work has significant practical significance for improving the macroprudential regulatory framework and the policy coordination system.

This study firstly integrates the mixed-frequency hierarchical dynamic factor model and the ICEEMDAN technology to realize the mixed-frequency monitoring and multi-scale feature recognition of China's financial security situation. Secondly, by using interpretation machine learning methods, the main short-term and medium-to long-term external risk factors threatening China's financial security are traced. Thirdly, based on the measurement of financial security and the analysis of the influence of external risk factors, the nonlinear local projection model is used to test the intertemporal regulatory effect of the two-pillar policy under the goals of security maintenance and risk prevention.

The research finds that with the process of high-level financial openness, the medium-term to long-term components of China's macro financial sovereignty and financial system's resilience have steadily increased, while the overall financial security and financial system's service capacity have shown small fluctuations. The intertemporal impact of imported inflationary shocks on overall financial security is more significant, while global economic policy uncertainty is the main medium-to long-term risk factor threatening macro financial stability, macro financial sovereignty, financial system's service capacity and resilience. Under the background of major events, there are significant differences in the impact of external risk factors on China's financial security. During the period of Sino-US trade frictions, the contribution of trade friction events increased. During periods of public health emergencies, the threat posed by global capital market shocks to overall financial security, macro financial stability, and macro financial sovereignty is significantly stronger. Two-pillar policy can help safeguard financial security, with macroprudential policy having a relatively better regulatory effect in enhancing overall financial security and macro financial sovereignty, while monetary policy is better suited to smoothing out the short-term negative impacts of major risk factors.

Based on the above conclusions, this paper puts forward the following policy recommendations. Firstly, under the guidance of a holistic approach to national security, continue to explore a financial security evaluation system and a dynamic financial security early warning system that conforms to national conditions, and effectively enhance the ability to capture external risk signals such as imported inflation and global economic policy uncertainty. Secondly, we should closely monitor the evolution of the global economic and financial situation and address key external risks in a targeted manner. By establishing a global risk early warning system, the ability of the financial system to resist and defuse external shocks can be enhanced. Thirdly, optimize the coordinated regulation mechanism and implementation path of macro policies to form a multi-level policy support system for safeguarding financial security. In this process, economic policies should not only focus on maintaining the financial security situation, but also match with various other planning objectives in the new development stage.