Generally in electric vehicles regenerative braking is incorporated to increase urban driving range on a single charge and to get the same brake torque as engine brake.In this paper analysis of the regenerative operation by thyristor chopper control is described.Firstly to clarify regenerative efficiency, the calculation of various losses such as commutation loss and thyristor loss which arises at braking mode is discussed, and it is described that the regenerative efficiency calculated from above losses agrees closely with test results. Secondly newly developed A.F.C. (Automatic Field Control) regenerative braking system is introduced. As in this A.F.C. regenerative control system, using shunt motor, field current is controlled inversely proportional to motor speed and regenerative operation is obtainable by low motor speed, this system is very suitable for electric vehicles.Thirdly it is noted that utilizing this A.F.C. regenerative brake control actual urban driving range can be increased by approximately 16%.