Abstract: On both sides of the Dadu River are high steep slope, and have high earthquake intensity, the slope stability come to the control factor on the selection of bridge position of the Luding Dadu river bridge on the highway from Yaan to Kangding. For the three planed bridge site, established the geological model and studied the slope stability and possible damage to the bridge. Research shows that the Shangba and Zhongba bridge site Ya'an shore slope are rock-soil and strong weathered rock slope structure, the soil and weathering rockmass will slide under seismic condition. There have through extraversion structure plane and large area of colluvial soil on the Kangding shore slope of Shangba and Zhongba bridge site, which are instability under the action of earthquake and difficult to control. On the Zali bridge site, the upper part of Ya'an shore slope are ancient river bed sediments, lower bedrock, sedimentary face nearly horizontal, the Kang'ding shore slope are moraine deposits.both side of the Zali bridge site are stable. Comprehensive analysis of three bridge site slope stability and the harm to the bridge, recommended to choose Zali bridge site.