The invention discloses a lubricating oil for gears. The lubricating oil is prepared from modified base oil, succinate, diethylenetriamine penta(methylene phosphonic acid), octyl diphenylamine, sorbitol, nano copper powder, C12 dibasic acids, beta-sitosterol, cholesteryl nonanoate, ethanediol amide cocoate and auxiliary additives. The lubricating oil for gears has the characteristics of favorable oxidation resistance, favorable corrosion resistance, favorable rust resistance, favorable wear resistance, favorable anti-friction property, high torque, favorable high-temperature stability, favorable demulsibility, long oil change period, favorable biodegradability and lower price than the traditional lubricating oil, and reduces the emissions of waste oil, waste gas and particles. The lubricating oil has the advantages of favorable viscosity, favorable lubricating property, favorable cooling property, excellent viscosity-temperature characteristics, high viscosity index, low condensation point and high flash point, and well reduces the friction between gear pairs.