The engineering geological characteristics of collapsible loess in Lanzhou New Area of Gansu Province are studied. Based on the complex stratum conditions of undisturbed loess hilly landform and field leveling project, the disease phenomenon and settlement observation data of high fill subgrade are analyzed. The harm of collapsible loess to high fill subgrade engineering in this area, and the specific design methods and precautions are summarized so as to provide reference for ensuring the engineering quality and reducing the road diseases of the similar projects.