The layout of drainage measures for deep-buried and long diversion tunnels is closely related to the seepage field and the external water pressure of the tunnel， which is an important measure to ensure the safety of surrounding rock and lining structure. Based on the deep buried long diversion tunnel of Dali section II of the water diversion project for the central area of Yunnan Province， ABAQUS numerical simulation method is applied to study the variation rule of the seepage field and external water pressure of the tunnel under different drainage schemes. The results show that the arrangement of drainage measures can effectively reduce the external water pressure of lining， but the reduction extent of water pressure in different parts of lining is different. The external water pressure on lining which is near drainage hole is greatly reduced. And the external water pressure on lining is reduced obviously with more drainage holes. The research results can provide reference for the design of the water control system for deep-buried and long tunnel in Southwest China.