Abstract: In order to explore the coupling effect of ferrofluid lubrication and dynamics of gear system, considering the excitation effect of external magnetic field and time-varying meshing stiffness, a ferrofluid lubrication model and a dynamic model were established to analyze the influence of magnetic induction intensity on ferrofluid viscosity, oil film stiffness, dynamic load distribution and lubrication characteristics. The results showed that the dynamic transmission error, vibration velocity and dynamic load can be reduced by appropriately increasing magnetic induction intensity and making the magnetic particles in the ferrofluid reach their saturated magnetization intensity, and hence the bite-into impact and tooth-change impact can be improved. The larger magnetic induction intensity reduced the temperature rise of oil film and increased the oil film thickness. When a large magnetic induction intensity was adopted, the amplitude of oil film pressure and the oil film thickness can be reduced, and the oil film pressure and oil film thickness tended to stabilize more quickly which means improved lubrication effect and suppressed vibration and noise of the gear system.