Abstract:United States is the founder of modern oil industry, which promoted the development of oil and gas in the world. By means of global layout of American oil companies, United States supercharges the backyard of North America while covets the forecourt of South America. United States realizes energy independence and opens energy hegemony during 70 years after World War II. On basis of reviewing the development history of American oil industry, this study analyzes the role of transnational oil and gas exploration, and development of Chinese national oil companies in ensuring national energy security. On the one hand, the entitlement oil and gas of overseas projects are operated back to China to secure national energy supply by international market, Chinese national oil companies shoulder the responsibility of making use of two markets and two resources. On the other hand, the foundation of upstream resources along China's strategic oil and gas corridors is consolidated by international oil and gas cooperation, Chinese national oil companies become the main force of propping up "Belt and Road" national initiative. China's oil and gas external dependence degrees are effectively reduced. In the context of profound changes unseen in centuries and the 21st century pandemic, aimed at the various challenges such as complexity and changes of global geopolitics, energy transition under China's "dual carbon goals" and all-round game between China and the United States, the related enlightenments and suggestions are put forward, which provide the references for "going out" of Chinese oil companies, sharing global oil and gas resources, and ensuring national energy security.