Abstract: The dynamic strength and accumulated deformation characteristics of subgrade filling are one of the most important factors affecting the normal operation of high speed railways. In order to demonstrate the applicability of red-mudstone as subgrade bed filling, static and dynamic triaxial tests are performed. Through the static triaxial tests, the strength and deformation characteristics of red-mudstone soil are studied, the strength indices are obtained, and that red-mudstone filling can meet the static requirments of subgrade is judged. Through the dynamic triaxial tests, the dynamic strength, critical dynamic stress, elastic modulus, damping ratio and accumulated deformation of red-mudstone soil under low confining pressure are studied. According to the analysis, it is concluded that the red-mudstone soil can be used to fill subgrade bed. It may provide reference for the application of red-mudstone in subgrade engineering.