Research conclusions ： (1) The collapse and uneven settlement are easy to appear to the foundation in collapsible loess area and the loess subgrade slope is the place where the water loss and soil erosion happen frequently. (2) In order to improve property and capacity of the deformation resistance of the railway subgrade in collapsible loess area and enhance the overall stability of the subgrade，the loess foundation must be treated specially and at the same time the slope protection must be conducted effectively. (3) The loess foundation treatment methods include the backfilling, the heavy rolling, building the sand cushion, heavy compaction, building geogrid and other forms. (4) The control of the Filling material is very important to the slope protection of loess subgrade and it incluses the controls of the particle size, moisture content, degree of compaction and so on. (5) The construction organization design presented in this paper, especially the measures for the subgrade reinforcement and the slope protection are available for the subgrade construction of heavy - haul railway in gravity - type loess area.