The climatologic mean and changes in cloud optical thickness (COT) of water and ice clouds in East Asia and their influence on the local radiation budget are studied quantitatively by using the Beijing Climate Center Radiative Transfer Model of BCC_RAD combined with satellite observational datasets from March 2000 to February 2018. Our results show that the annual mean COT over East Asia decreases from the southeast to the northwest, and the annual mean COT of water (COT_w) and ice cloud (COT_i) in this region are 15.0 and 11.6, respectively. The anomaly variations of COT illustrate that the variation intensity of COT_w is stronger than that of COT_i. Moreover, COT varies with sub-regions and seasons in East Asia. The trends of COT_w in the northeastern and southern China are found to be 0.022 yr^-1 and -0.071 yr^-1, respectively, while the COT_i trends over the two regions are 0.062 yr^-1 and -0.009 yr^-1, respectively. The annual mean shortwave-, longwave-, and net-radiative effects for the 18 years caused by water clouds in East Asia at the top-of-atmosphere (TOA)/surface are -72.4/-97.9, 15.7/31.1, and -56.7/-66.7 W m^-2, respectively. The corresponding effect caused by ice clouds are -88.5/-107.5, 55.7/12.2, and -32.7/-95.3 W m^-2, respectively. The shortwave cloud radiative effects (CREs) dominate the longwave CREs not only at the TOA but also at the surface, and the effects of COT_i changes on the radiative budgets are stronger than those of COT_w over the East Asia region.