Abstract: Transit transportation of oil & gas is critical to energy supply. In view of the Ukrainian oil & gas transportation system, the transportation problem of Russian oil and gas transit through Ukraine was analyzed, with the internal relationship between Ukraine as a transit country and its relationship with Russia revealed, and recommendations for strengthening the security of China's oil & gas transportation routes were proposed. The research shows that, Ukraine's oil & gas transportation system is very huge, consisting of about 4.3 × 10⁴ km of oil & gas pipelines, with the transit capability of 5 630 × 10⁴ t/a for oil and 1 460 × 10⁸ m³/a for gas. Ukraine is strategically located and has a strong transportation system, and from the perspective of economy and technology, transit through Ukraine is the most convenient route for Russian oil & gas transportation to Europe. However, the high dependence of Russia on Ukraine enables the latter to create a corridor power, which also becomes a weapon of geopolitical game between Ukraine and Russia. In order to ensure the security of energy transportation, Russia has constructed the oil and gas pipelines crossing the Baltic and Black Seas with Ukraine bypassed, realizing the control of energy transportation corridor. As the largest importer of oil & gas in the world, China is building an oil & gas transportation system gradually. Further, the awareness of potential risks of transit transportation of oil and gas should be enhanced, and attention should be paid to the research on the issues of the oil & gas transit countries in view of geopolitics. By optimizing the transportation routes pattern and transmission capacity configuration, the transportation routes should be developed in a diversified way and the emergency response capability of the oil & gas transportation system should be improved.