To accurately predict the temperature distribution of a pair of gears under oil injection lubrication, a series of steps are followed. Firstly, the heat flux distribution on the friction tooth surface of the gear is obtained through transient calculation. This data is used to solve for the gear surface temperature distribution under steady state conditions. Subsequently, a heat-fluid-solid coupling model is established in Fluent to determine the convective heat transfer coefficient of the gear surface. Through an iterative process, the gear surface temperature and the gear surface convective heat transfer coefficient are refined until convergence is achieved. The obtained temperature field distribution of the gear is then compared with experimental results to verify the accuracy of the model. The effects of different injection pressures on the gear surface temperature are also analyzed and compared with experimental results. The results show that the numerical model effectively predicts the temperature field of gears under oil injection lubrication, with the error between the simulation and experimental results being within 3.5%. This is valuable for future research on the surface temperature distribution of gears under oil injection lubrication.