Abstract: The transposition technique of stator bars in the large generators is one of the key techniques in hydro-generator design. Currently, the calculation of circulating current losses generally adopts the leakage susceptible electric potential method, but there has a large limitation that excessive simplifications and assumptions of leakage flux in slot and end are existed in the process of the calculation. Therefore, the method of 0°/360°/0° stator bar transposition with void was mainly discussed by the three dimensional finite element method coupled field-circuit. What’s more, the calculation accuracy of the circulating current losses of hydro-generator stator bars was verified by the experiment. The circulating current and the circulating current losses of each stator bar strand adopted different lengths of transposition with void were calculated accurately. The disadvantage of traditional transposition with void was found, and then a new combination transposition method was put forward. The calculation results show that compared with the method of 0°/360°/0° stator bar transposition with void, the circulating current losses of hydro-generator stator bars is decreased significantly with the new combination transposition method, and the effectiveness for reducing circulating current losses of generator stator bars is verified.