The invention discloses a method for reinforcing aeolian sandy soil by polypropylene fibers. The method comprises the following steps: selecting materials for preparing fiber aeolian sandy soil, wherein the length of the polypropylene fiber is 18mm, the mix ratio of the fiber is 0.3 percent, and the aeolian sandy soil materials are air-dried aeolian sand or aeolian sandy soil (the moisture content accounts for 11.2wt%); according to the proportioning scheme, closely and completely mixing fine TEXSOL with aeolian sandy soil particles by way of spraying, so that a composite three-dimensional spatial structure is formed by the TEXSOL and the aeolian sandy soil; and carrying out mechanical compaction on the composite fiber aeolian sandy soil subjected to spraying, wherein the compaction method and standard of the composite fiber aeolian sandy soil are same as those of common soil, so that the compaction density of the aeolian sandy soil reaches 100 percent of the standard compaction density, and the fiber aeolian sandy soil is compacted closely. By utilizing the method in earth-filled dams, retaining walls and the drainage works of the earth-filled dams, the water stability of the interior of the soil body can be effectively improved, the shearing strength and tensile strength of the soil body can be obviously improved, and the construction process is simple; and because the fiber content of the fiber aeolian sandy soil is very low, the method has the advantages of cheapness and environmental protection.