The effect of magnetic particle volume fraction on the lubrication performance of ferrofluid solid-liquid interface was studied by molecular dynamics simulation.The ferrofluid model of Fe3O4 with volume fraction of 5%,9.6% and 14.7% was established,and the ferrofluid solid-liquid interface lubrication model was constructed.The structure of the lubrication model was optimized and annealed,and the optimized model was simulated.The simulation results show that with the increase of the magnetic particle volume fraction,the friction coefficient is reduced,so the lubrication performance of the ferrofluid is improved.The friction coefficient of the ferrofluid with volume fraction of 14.7% magnetic particles is about 67% lower than that of the ferrofluid with the volume fraction of 5% magnetic particles.Based on the data of mean square displacement, kinetic energy, van der Waals potential energy and temperature change,the effect of magnetic particle content on the lubrication performance of ferrofluid was explored from a microscopic point of view,and the mechanism of the effect of magnetic particle content on the lubrication of ferrofluid solid-liquid interface was revealed.The results show that the increase of magnetic particle content will enhance the diffusion ability of molecules in the magnetic fluid, make some molecules in the magnetic fluid adhere to the surface of the solid layer,and form a penetration layer or diffusion layer with strong friction reducing and anti-wear,so as to improve the lubrication performance of the magnetic fluid.In addition,the increase of magnetic particle content will reduce the van der Waals force between molecules in the magnetic fluid,change the viscosity of the magnetic fluid,and enhance the thermal conductivity and heat transfer performance,so as to improve the lubrication performance of solid-liquid interface.