Abstract: Aiming at complex geological conditions such as high-intensity earthquake areas，complex terrain and geological conditions，and dense development of unfavorable geological conditions,the location of important bridges that cross the river should be selected with priority-geological conditions are the key to bridge location selection. Taking the site selection of Dexing Bridge in Motuo County，Xizang as an example，combining the characteristics of the river bank of the project area and the engineering geological environmental conditions,the principle of site selection for the bridge across the river was drawn up，and the UAV assisted investigation ，engineering geological mapping，enginecring geophysical prospecting ，and geological drilling were adopted. And other comprehensive survey methods，focusing on the study of the engineering geological conditions of the river reach，through multi-program comparison analysis，to determine the recommended bridge location that is technically feasible，risk controllable，investment-saving，and easy to construct，which can provide bridge location selection for similar bridge projects reference.

Key words: complex geology condition, bridge site selection, comprehensive comparison and selection