The invention relates to mechanical lubricating oil and a preparation method thereof. The mechanical lubricating oil is prepared from the following raw materials in parts by weight, 3-5 parts of silane coupling agents, 1-3 parts of machine oil, 4-7 parts of alkenyl succinic acid, 1-3 parts of sodium citrate, 2-5 parts of hydrochloric acid, 2-5 parts of sulfuric acid butyl-octyl alcohol zinc salt, 1-3 parts of antioxidants, 4-6 parts of triethanolamine, 2-4 parts of monosuccinimide and 1-3 parts of stearic acid monoglyceride. The mechanical lubricating oil has the advantages that mechanical friction is decreased, mechanical abrasion is resisted, frictional resistance is reduced, energy sources are saved, abrasion is decreased, mechanical service life is prolonged, economic benefits are improved, mechanical rusting can be prevented, viscosity of the lubricating oil is effectively adjusted, and a machine is prevented from being oxidized and corroded.