Ball bearings are widely used in automotive driveline systems, and their performance plays a crucial role in driveline safety and transmission efficiency. However, the studies on revealing the internal flow mechanism of ball bearings and predicting the churning power loss under jet lubrication system are still insufficient. In this study, a numerical simulation model consisting of a bearing chamber, balls, and nozzles was developed. The flow under a series of operating conditions was simulated and the effects of different injection angles on the lubrication performance of the bearing were analyzed. In addition, a churning loss prediction model was established by constructing an orthogonal scheme, magnitude analysis and multiple linear regression, and a bearing churning loss test rig was built to verify the accuracy of the prediction model. The results show that the lubrication effect is enhanced when the nozzle is facing the inner ring; The influence of oil temperature on the churning torque is greatly weakened at higher flow rates, while it is opposite at lower flow rates; 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 internal flow mechanism of ball bearings under the oil injection system and provides a method to predict the oil churning power loss of ball bearings.