Abstract: The mechanical behaviors of polypropylene fiber reinforced red clay are studied by means of different test methods. The compaction test and the permeability test show that the maximum dry unit weight of the fiber reinforced red clay is basically a constant value and the variation range of the optimum moisture content is great with certain fiber content. It has the same magnitude of permeability coefficients as the fiber reinforced red clay and the permeability coefficient is small. The results of direct shear test, unconfined compressive test and triaxial consolidation undrained test show the strength of the fiber reinforced red clay is obvious higher than that of the red clay, which increases with the fiber content and length. After being mixed with fiber, the cohesion of red clay rises a lot and the change of friction angle is small. The stress-strain curve of the fiber reinforced red clay shows typical work hardening character. The sample has the character of bulging breakage.