Serious drought occured in the central area of Xizang Autonomous Region in the early summer of 1992. Analyses show that the main circulation backgrounds are as the following. The subtropical high laid further south ,while its seasonal movement northward was much later. The circulation over the Qinghai-Xizang Plateau adjusted later from spring to summer. The India monsoon low deepened eruptively later, and its intensity was weaker. When the south Asia high first reached the Qihai-Xizang Plateau, it's delayed. The system of shear lines was weaker and laid to the north.