In 2013, China imported 282 million tons of crude oil with an external dependence of 58.1%, surpassing the USA as the world’s largest net oil importer. An import source diversification strategy has been adopted by China to ensure oil supply security and to prevent oil supply disruption. However, the strategy is restricted by the imbalance of oil reserves. What is the reasonable and clear objective of the diversification strategy under an imbalanced environment? How do we assess the natural imbalance? This paper analyzes the oil import diversification of China and the USA, as well as the oil production of oil export countries by the oil import source diversification index (OISDI). Our results are as follows: the distribution of oil import sources for China tends to coincide with the oil production distribution of oil exporters in the world. Compared with the USA, China has more diversified import sources. The Chinese government paid much attention to import sources in the past. In the future, China will adjust the distributions of regional sources rather than focus on the number of sources to further optimize the structure of imported regions in the course of implementing the import source diversification strategy.