Abstract: The fissure orientation is one of the important factors contributing to the anisotropy of mechanical properties of expansive soil. To explore the influences of inclination angle of fissures on the dynamic properties of soil, using the undisturbed expansive soil with different inclination angles of fissures (α=0°, 22.5°, 45°, 67.5° and 90°) in the PiShihang Irrigation Area of Anhui Province as the research object, the unidirectional cyclic load tests are carried out on the soil by using the GCTS dynamic and static true triaxial instruments. The effects of fissure inclination, confining pressure and different dynamic stress amplitudes on the characteristics of the cumulative plastic strain, dynamic elastic modulus and damping ratio of expansive soil are studied. The test results show that as the amplitude of cyclic loading increases, the cumulative strain of the samples with the same fissure angle increases continuously. Among the studied five fissure angles, the sample withα of 67.5° produces greater cumulative plastic strain at each amplitude of cyclic loading. Under low confining pressure, the fissure angle greatly influences the critical dynamic stress amplitude of the soil, and its anisotropy characteristics are significant. As the confining pressure increases, the anisotropy of the soil weakens. With the increase of the fissure angle, the dynamic elastic modulus of the sample shows a trend of decreasing first and then increasing. When α = 67.5°, the dynamic elastic modulus of the sample is the smallest, and the dynamic elastic modulus decreases rapidly when the amplitude of the cyclic vibration load increases to the critical dynamic stress. According to the characteristics of the damping ratio changing with the number of vibrations, an expression model considering the characteristics of the attenuation rate, initial damping ratio and stable damping ratio is proposed, and the influences of dynamic stress amplitude and confining pressure on the variation of damping ratio are analyzed. The research results are of great significance for revealing the anisotropy of the mechanical properties of fissured expansive soils under dynamic loads and ensuring the safe operation of railway routes and rail transits in expansive soil areas.