In the present work, physical property, film-forming property, and tribological performance of three trimellitates and their blends with polymethacrylates viscosity modifiers were investigated. The results showed that the addition of polymethacrylate can significantly improve the viscosity and low temperature fluidity of the base fluids, while exerting slight influence on the viscosity-temperature properties and film forming performance. Tribological tests showed that under boundary lubrication conditions, polymethacrylate modified lubricants exhibit better friction reducing properties over a wide range of temperature and load. However, under high temperature or high load, the performance is weakened. This phenomenon should be due to the formation and destruction of the physically absorbed layer of the polymethacrylate polymer molecular on the metal surface. Under moderate boundary lubrication conditions, the physically absorbed layer can effectively prevent the direct contact of rubbing surface, resulting in a reduction of friction coefficient, while under more severe boundary lubrication conditions, the adsorbed layer is destroyed and the friction coefficient increases again.