China and the United States (U.S) produce approximately one-third of global economic output, and emit more than two-fifths of global total carbon emissions. Comparing the decoupling of economic growth from carbon emissions in China and the U.S. can inform the development of effective mitigation strategies for those two countries and the world. In this study, we compared both the carbon emissions performance and the decoupling performance between China and the U.S. We quantified the decoupling status in China and U.S. using the Tapio decoupling indicator, and decomposed the decoupling index to explore the driving factors affecting the decoupling using the Logarithmic Mean Divisia Index (LMDI) technique. The results show that China experienced expansive coupling and weak decoupling in most years between 2000 and 2014; the U.S. experienced mostly weak and strong decoupling. In general, income and population effects restricted decoupling, whereas the energy intensity and energy mix effects promoted the decoupling process in China and the U.S. In addition, the carbon intensity effect exerted negative and positive effects on decoupling in China and the U.S., respectively.