Abstract: In this paper, two kinds of versatile additives were synthesized, namely DDMA and CDMA, with different chain lengths, and applied them to lithium complex grease. The physicochemical properties, antioxidant properties and tribological properties of the lithium complex grease were systematically studied. The dropping point, cone penetration and oil separation under pressure of the grease with different concentrations of DDMA and CDMA were investigated according to the standard test methods; the antioxidant capacity of DDMA and CDMA in the lithium complex grease was tested by differential scanning calorimetry; the reducing friction, anti-wear and extreme pressure performance of DDMA and CDMA on the lithium complex grease under different concentrations and loads were investigated by a microcomputer-controlled four-ball long wear test machine and a four-ball friction test machine. The test results showed that the influence of DDMA and CDMA additives on the dropping point of the grease was not significant, and they exhibited comparable performance with the base grease; the cone penetration gradually decreased with the increase of concentration, and the grease became harder, which might be due to the additive molecules had undergone chemical reactions with the fiber structure in the base grease, enhancing the network structure of the base grease and improving its shear resistance; the control oil capacity of the grease was improved with the increase of DDMA and CDMA concentration, which might be because the base oil was trapped in the network structure and could not be released, losing its fluidity. DDMA and CDMA could increase and prolong the initial oxidation temperature and oxidation induction time of the base grease at 200 ℃. DDMA and CDMA could significantly improve the reducing friction and anti-wear performance of the base grease, enabling the base grease to stably maintain a low friction coefficient (0.05) and wear scar diameter (0.39); under different loads (588 N), CDMA had better low friction (0.06) and anti-wear (0.41) performance than DDMA and the base grease, which could significantly improve the high friction situation of the base grease under high loads, indicating that CDMA had good lubrication effect in a wide load range. CDMA and DDMA could effectively increase the P_B (1 569 N) and P_D (1 961 N) values of the base grease, and they showed comparable performance between DDMA and CDMA. At a mass fraction of 1%, CDMA had better load-bearing capacity compared to DDMA and the base grease. The worn surface morphology of the steel ball after lubrication was analyzed by scanning electron microscope (SEM), X-ray energy spectrometer (EDS) and non-contact three-dimensional profilometer (3D), and the chemical composition of the worn surface was analyzed by X-ray photoelectron spectrometer (XPS). The characterization results indicated that the addition of DDMA and CDMA could effectively reduce and minimize the furrows of the base grease on the worn surface, making the wear scar of the base grease smaller and rounder; three-dimensional analysis revealed that DDMA and CDMA made the surface of the base grease smooth and flat. The lubrication mechanism showed that the carboxyl groups in DDMA and CDMA molecules adsorbed on the friction pair surface. Under the action of friction heat, the additive molecules undergone tribo-chemical reactions with the iron surface and generated protective film containing FeS₂, Fe₂O₃, Fe₂(SO₄)₃, organic phosphate and aromatic compounds. This protective film prevented direct contact between metals, thereby achieving the effect of friction reducing and anti-wear.