Abstract: How big are the areas the China’s frontiers cover? The paper begins with this topic, and reveals that the basic feature of China’s frontiers is its characteristics of various ethnic groups living there. It further proposes that, based on the fact that geographically a large part of China’s frontiers is in the location of the Inner Asia, the ethnic characteristics of China’s frontiers reflect the special attributes of the inner Asia as well. Therefore, when defining what is meant by China, one must not lose sight of the implications of Inner Asian elements within it.