Abstract: In the summer time of Wulanaodu region, changes of directive radiation with slope gradients are gentle on south, southeast and southwest facing slopes, but sharp on north facing slope. The hottest slope gradient (gradient with maximum directive radiation) increases as slope dlreetions aFFroaeh the south. In winter,directive radiations reduce rapidly from south to north facing slopes, the reduction becomes greater as slope gradient increases. Directive radiations increase with increasing slope gradient in all slopes to the south,and reduce gradually after they surpass the hottest gradient of the slope.