The underlying strata of some tunnels in Nanchang Metro are all weathered mud siltstone, which is easy to be destroyed under the repeated action of groundwater and train load for a long time, affecting the stability of the tunnels. To this end, a series of cyclic dynamic triaxial tests were carried out on the rock samples, and the parameters of confining pressure, dynamic stress state, load frequency and cyclic loading times were analyzed in detail. The results show that the application of confining pressure can enhance the structural densification of rock samples and improve the ability of rock samples to resist deformation, while the water infiltration and the initial static deviating stress can make the structure of rock samples loose, reduce the strength, and aggravate the damage degree. In addition, increasing the amplitude of dynamic stress and decreasing the frequency of dynamic stress will also lead to lower strength and higher deformation degree of rock sample. With the increase of cyclic vibration times, the axial cumulative strain increases gradually, and the attenuation coefficient of shear modulus decreases gradually. When the vibration times exceeds 2000, the increase amplitude of axial cumulative strain and the attenuation change of shear modulus decrease significantly and gradually tend to be horizontal.