We used a new conceptual framework that integrates tenets from health economics, social epidemiology, and health behavior to analyze the impact of socioeconomic forces on the temporal changes in the socioeconomic status (SES) gap in childhood overweight and obesity in China. In data from the China Health and Nutrition Survey for 1991 to 2006, we found increased prevalence of childhood overweight and obesity across all SES groups, but a greater increase among higher-SES children, especially after 1997, when income inequality dramatically increased. Our findings suggest that for China, the increasing SES gap in purchasing power for obesogenic goods, associated with rising income inequality, played a prominent role in the country's increasing SES gap in childhood obesity and overweight.