To evaluate the simultaneous meshing of gear pairs, the contact ratio is an important index. Super-High- Contact-Ratio (SHCR) helical gear transmission has the advantages of strong bearing capacity, stable transmission, low vibration and noise, and is widely used in ocean engineering, aerospace and other fields. Both the influence laws of gear macro-parameter on the transverse contact ratio and axial contact ratio of SHCR helical gear, and different transverse contact ratio, axial contact ratio and contact line length change rate on time-varying meshing stiffness (TVMS) are investigated in this paper. Then, a rigid-flexible coupling dynamic model of SHCR helical gear transmission system is established, and the effect rules of transverse contact ratio and axial contact ratio on the vibration characteristic of the system is obtained, which provides a theoretical basis for the vibration reduction design of the gear transmission system.