Based on coupled heat transfer theory, a model of turbine box with waste gate was built, and turbine box, heat shield and bearing body was tied as an assembly to be heat transfer analyzed. Temperature and thermal stress analysis of bearing body were then obtained. The results show that temperature is gradually reduced from turbine box to bearing body, which presents an obvious temperature gradient. And the temperature of turbine box is about 71.5℃ lower than original gas temperature. Because of good insulation of heat shield and dual cooling of cooled water and oil, the temperature of bearing body is low. However, the thermal stress of bearing body is high due to its temperature difference between inside and outside surface. Compared with the test results, the maximum deviation between the simulated and experimental value is 7.2%, which verifies that this simulation method has high precision and can provide a theoretical basis for the design and optimization of turbocharger.