This article presents a matrix to analyze the ethnic identity of children from interethnic marriage families. Based on the population balance equation, this study uses individual level data from the seventh national population census to estimate the net effects of ethnic identity on the population change between 2010 and 2020 and examine the preferences among different ethnic groups. An increase of approximately 8.57 million children were from interethnic marriage families over the decade, with nearly 40% of the ethnic minority increase experiencing ethnic identity choices. The size of net population increase due to ethnic identity choices of the ethnic minority was about 1.95 million, accounting for about one-tenth of the increase in the ethnic minority population. For children from Han-minority intermarriage families, about 79.33% had ethnic minority identity. The population changes among different minority groups were mainly driven by the sizes and preferences of children from Han-minority intermarriage families. There were variations in interethnic preference among different interethnic marriage circles.