This paper mainly studies the power losses in a refined two-speed dual clutch transmission which is equipped in a electric vehicle test rig. Both numerical and experimental investigations are carried out. After theoretical analysis of the power losses original sources, the developed model is implemented into simulation code to predict the power losses. In order to validate the effectiveness of the proposed model, results from experimental test are used to compare the difference the simulation and test. The simulation and test result agree well with each other. Results show that the power losses in the two-speed are mainly generated by multi-plate wet clutch drag torque and gear churning loss.