Abstract: Based on statistical facts, the heat source variation of the Qinghai-Xizang Plateau is related with the flow of upper reaches of Yellow River. A numerical experiment of influence of the heat source variation over the Qinghai-Xizang Plateau on the flow of upper reaches of Yellow River in the summer is performed with a model of GCM. The results show that while the heat source of the Plateau is weaken, the runoff is decreased and flow is descended. As a result, the heat source vaiation of the Qinghai-Xizang Plateau is one of the important causes which led to flow variation of the upper reaches of Yellow River