The land border areas are key regions for the country to maintain territorial sovereignty, integrity, and security. Since the new century, China has made great achievements in its modernization drive, greatly improving its national strength, and fundamentally altering its border security situation. At the same time, the trend of regional population increase and decrease in China has been directly reflected in these border areas. The seventh national census data show that the total population in border areas across the country has begun to decrease, which has attracted widespread attention from Chinese society. Based on census data, the population change trends in border areas are presented, and the current security situation faced by China's border areas is analyzed. The research results indicate that the current population changes in China's border areas are an inevitable result of China's modernization process and will not adversely impact national defense and security in these areas. In the new era, we need to accelerate urbanization in border areas, reduce the populations engaged in agriculture and animal husbandry, improve the level of economic and social development in border areas, leverage China's modernization to drive the common development of neighboring countries, jointly build a community of shared future for mankind on both sides of the border, and create a higher level of security and stability in border areas.