The invention provides a slide rail grease composition and a preparation method thereof. The composition comprises 75-80% of base oil, 10-15% of a composite lithium and calcium base thickener, 0.2-1% of an antioxidant, 1-5% of an antirust agent, 1-3% of an extreme pressure anti-wear agent, and 1-3% of a solid lubricant, wherein the base oil comprises mineral oil and poly-alpha-olefin, the viscosity of the poly-alpha-olefin at 100DEG C is 10-40mm<2>/s, and the viscosity of the mineral oil at 100DEG C is 4-10mm<2>/s. The composition obtained through compatibility of above components with above contents has excellent anti-rust, anti-wear and adhesion properties at -40-150DEG C. Experiment results show that the dropping point of the composition is 272-295DEG C; the composition has no black or green change after copper corrosion; the water resistance is 1-2%; the low-temperature starting torque is 0.28-0.42N.m; the low-temperature movement torque is 0.15-0.19N.m; the maximum nonseizure load is 1079N, and the sintering load is 3090N.