Abstract: Water diversion project in central area of Yunnan Province is a key long-distance diversion project in the 13th Five-year Plan of China. Water-conveyance tunnel is the most important structure for water delivery and has such characteristics as large quantity, different?lengths, various diameters, complex geology conditions. Because the tunnels along the project were designed by different companies, and there was no specific monitoring design code for tunnels in China, it is easy to cause great difference in instrument arrangement of various tunnel sections. Based on the section “Hydraulic Tunnel Monitoring” in the safety monitoring specification for water conservancy and hydropower projects(SL725-2016), and through in-depth analysis on the layout, structure, stress and geological conditions of the tunnels, the principles for selecting monitoring items and monitoring sections were formulated, and the principle of detailed layout of monitoring facilities was put forward. So far, these design principles have been fully implemented as guiding basis for tunnel monitoring design in that water diversion project. It effectively guarantees the standardization of tunnel monitoring design and improves the design quality, which has great reference value for monitoring design of similar projects.