With the rapid growth of China’s energy consumption and the great pressure on reduction of carbon emissions, natural gas is an increasingly valuable energy source for enhancing energy and environmental sustainability. To sustain external natural gas supply, China has constructed a series of gas pipelines and liquefied natural gas (LNG) terminals for the increasing gas importation. This article identified five gas corridors of China: Central Asia–China gas pipelines, Myanmar–China gas pipelines, Russia–China gas pipelines, Australia/Southeast Asia–China seaborne LNG shipment, and Middle East/North Africa–China seaborne LNG shipment. It then proposed a group of indicators that may influence the security of China’s external gas shipment from a supply chain perspective, and composed them into a Risk Index for assessing the corridors of China’s natural gas importation using the Fuzzy AHP and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods. The results indicate that (a) transport distance, geopolitical risk, and resource risk are the major obstacles for China’s natural gas importation; (b) China’s natural gas importation is experiencing a mid-level risk, and the gas pipelines from Central Asia, Myanmar, and Russia are the most secure gas corridors for China, while LNG shipment from Middle East and North Africa has the greatest risk index. (c) China’s diversification strategy has been successful, but a more balanced strategy is suggested to deal with the high gas dependence on Turkmenistan and Australia, as well as Russia when the cross-border gas pipelines are completed and fully utilized in the near future.