Taking the battery module bus-bars of an electric vehicle as the research object, the 3D digital of bus-bar, working boundary conditions, connection relationships between bus-bar and battery cells were extracted. The influence rules of current size, convective heat transfer coefficient and pole welding process on the temperature of bus-bar were studied by numerical method of thermoelectric coupling. In order to ensure the accuracy of the numerical calculation, the dynamic battery pack test system was used to investigate the temperature variance of the specified working condition. The test condition was consistent with the boundary setting in the numerical calculation. The results show that the grid partition, boundary condition, current size, convective heat transfer coefficient and pole welding process have different effects on the temperature rise of the bus-bar. As the error between the numerical calculation and test result occurs in some working conditions, the reason was analyzed in detail. The correlation between the factors and the influence law of the error were also further studied, and then the numerical calculation model was modified. Finally, under the new working conditions, the numerical calculation and experimental measurements of bus-bar were carried out. Through using factor association and the influence rule on the error, the error between numerical calculation and experimental measurement was within 3.7%.