We used the observed CO/<sup>222</sup>Rn ratio in Asian outflows at Minamitorishima (MNM), Yonagunijima (YON), and Ryori (RYO) over the Western North Pacific from 2007 to 2011, together with a three-dimensional chemical transport model (STAG), in order to estimate anthropogenic emissions of CO in East Asia. The measurements captured high-frequency synoptic variations of enhanced <sup>222</sup>Rn (ERN) events associated with long-range transport of continental air masses. <sup>222</sup>Rn and CO showed high correlation during the ERN events observed at MNM and YON in the winter and spring, but not at RYO. The STAG transport model reproduced well the concentration of observed <sup>222</sup>Rn when forced with constant and uniform flux density of 1.0 atom cm<sup>−2</sup> s<sup>−1</sup>, but underestimated the associated enhancement of synoptically variable CO caused by the underestimated flux values in the EDGAR ver. 4.1 emission database used in the model for East Asia. Better estimates for the East Asian emission were derived using a radon tracer method based on the difference in the enhancement ratio of CO/<sup>222</sup>Rn between observation and model. The anthropogenic emission of CO for China, Japan, and Korea was estimated to be 203 Tg CO yr<sup>−1</sup>, 93% of which originated in China. When compared with other estimated emissions of CO, our estimated result showed consistency with those of the inverse method, whereas the emission database of EDGAR was about 45% smaller than our anthropogenic estimation for China.