Energy security is important for the security system of a country. Affected by global geopolitics and the COVID-19 pandemic, China’s energy security is currently facing severe challenges. Reducing the import scale of oil and gas based on the comprehensive and efficient utilization of domestic energy to ensure energy security remains a topic that requires research for promoting China’s high-quality and sustainable development. This study first reviews the evolution of the energy security concept and summarizes the energy security strategies of typical countries. Then the energy security in China is defined from five dimensions: sustainable development, guaranteed supply, scientific support, economic affordability, and guaranteed system. Moreover, the situation faced by China’s energy security is studied and corresponding strategies are proposed. We propose that China should make efforts to stabilize the production of traditional energies, ensure the supply of imported oil and gas, promote renewable energy consumption to complement the current energy mix, encourage cooperative innovation of energy science and technology, and improve the energy development mechanism. Furthermore, we propose several policy suggestions to ensure China’s energy security from the aspects of top-level plan, integrated development of gas and renewable energies, scientific innovation of renewable energies, and international cooperation.