Abstract: To understand the dust aerosol effects on climate quantitatively, we have calculated the global distribution of direct radiative forcing due to dust aerosol under clear and cloud sky for winter and summer, by using an improved radiative transfer model and the global distribution of dust mass concentration given by GADS (Global Aerosol Data Set). The results in this paper show that the global means of the solar forcing at tropopause for winter and summer are -0.477 and -0.501 W/m2, respectively; the corresponding values for the longwave forcing are 0.11 and 0.085 W/m2, respectively. At the surface, the global means of the solar forcing are -1.362 W/m2 for winter and -1.559 W/m2 for summer, whereas the corresponding values for the longwave forcing are 0.274 and 0.23 W/m2, respectively. It points out by this work that the absolute values of the solar forcing both at tropopause and the surface increase linearly with the cosine of solar zenith angle and surface albedo. Solar zenith angle influences both of the strength and distribution of the forcing greatly. This study shows that cloud takes great effects on the direct radiative forcing of dust, which depends on many factors including cloud cover, cloud height, cloud water path, surface albedo, and solar zenith angle etc. Of all, the effects of low clouds and middle clouds are larger than those of high clouds. The existence of clouds reduces the longwave radiative forcing at tropopause, in which the influences of low clouds are the most obvious. Therefore, the impacts of cloud should not be ignored when estimating the direct radiative forcing due to dust aerosol.