Spiral bevel gears are widely used in automobile transmission systems, and their performance plays a crucial role in driveline safety and transmission efficiency. However, studies on the lubrication performance and churning power loss of spiral bevel gears under an injection lubrication system are still insufficient. In this study, a numerical simulation model consisting of a nozzle, a spiral bevel gear pair, and a box was developed. The effects of different injection velocities, nozzle diameters, oil temperatures, and injection angles on the lubrication performance were simulated and analyzed. In addition, a churning loss prediction model was established by constructing an orthogonal scheme, dimensional analysis, and multiple linear regression, and a spiral bevel gear churning loss test rig was built to verify the accuracy of the prediction model. The results show that the injection velocity and nozzle diameter have a more pronounced effect on the oil volume fraction on the gear surface, while the lubricant temperature has little effect on it; the relative error between the predicted and experimental values of the established model is within 10%, which meets the industrial requirements. This work helps scholars to understand the lubrication mechanism of spiral bevel gears and provides a method to predict the churning power loss of spiral bevel gears under oil injection systems.