Fracture mechanics analysis of the Dynamic Stress Intensity Factor of a pre-cracked 3-Point Bending Specimen suffering cyclic loads has been studied. Using the theoretical equivalent system of the pre-cracked 3-Point Bending Specimen, the Dynamic Stress Intensity Factor could be obtained theoretically. The finite element method was then applied to study the dynamic behaviors of the Dynamic Stress Intensity Factor under different cyclic loads' conditions using the standard software ABAQUS. The results have also been analyzed and discussed, which provided a deeper view for the fracture characteristics of the materials and could be used to guide further researches and practical engineering design.