Abstract: Lithium base grease was prepared in laboratory. Different composites of ultrafine silicon material (Si-Al type) and Zn powder were designed as the Lithium base grease additives. The four-ball friction tester was used to investigate the influence of different composites on the tribological properties. The results were compared with that of the market additives. The worn surfaces were analyzed by means of optical microscope (OM) and energy dispersive X-ray Detector (EDX). The results show that the tribological properties of the composite powders were more excellent than that of the base grease and market product additives. Compared with base grease, the wear scar diameter and the average friction-coefficient using the composite additive (0.5%Zn/0.5%(Si、Al)) was reduced by 54.97% and 23.62%, respectively, at 588N loading. The analysis of the instant changes of friction-coefficient shows that the amplitude of the friction factor can be effectively reduced by the composite powder, which is helpful to reduce the noise and enhance the steady ability of machine. EDX show that a lubricating film mainly composed of SiO2 and Zn is formed on the worn surface that has notable tribological properties.