Abstract: By using Q-vector analysis of the process of shear line formation over the Qinghai-Xizang Plateau on 1—6 June 1982, which is triggered from a moving trough aloft, it is found that the favorable situations are: (1) the shear line on the Plateau is formed and maintained in a convergent zone extending from east to west at the 500 hPa Q-vector field where ▽? Q＜0, and at 200 hPa ▽? Q＞0; (2) a wide area of ascent current is an important role of formation and maintenance of the shear line; (3) the formation and existance of shear line over the Plateau is connected with frontogenesis to certain extent.