In helical gear lubrication and transmission, high precision and stability are its advantages. However, the vibrations and cavitation caused by high speeds pose a great risk to helical gear drives. Based on this, this paper proposes a helical gear cavitation model that couples gear dynamics and cavitation two-phase flow, with the relative displacement caused by vibration as the model coupling node. The model accuracy is adjusted according to the experimental results, and the geometry and operating conditions of helical gears are considered comprehensively. The simulation results show that the cavitation vapor distribution is affected by the slant of the contact line of helical gears, and the cavitation intensity and the degree of oscillation are more serious at high speed and light load.