Research conclusions :(1) Within the area of expressway, the debris flow has the characteristics of breaking out with numbers, large area, high frequency and high truculency. (2) Debris flow distributed along the proposed expressway has the damage modes of buried hazards, destroyed hazards and blocking river hazards. (3 ) In the area of valley, the engineering geological alignment of the proposed expressway should be done before ascertaining the traces of debris flow activity and its scale，and then determined the position and elevation of the expressway ； The alignment of the proposed expressway should avoid the debris flow which is in the period of formation and development，or is afflicted by serious silting ； In the valley area the alignment of the expressway should be prohibited passing through the position of debris flow deposit，but allowed to cross the flowing area of debris flow by the form of high - span bridge. (4) The research conclusions can be widely applied in the geological alignment for expressway，railway engineering in Wenchuan area.