This paper presents a sensorless algorithm for the vector control of doubly-fed induction machine（DFIM） using rotor current based model reference adaptive system（MRAS） observer. The stator flux oriented vector control is employed to achieve variable-speed drive and decoupled active/reactive power control. In the proposed MRAS observer， the reference model is the measured rotor current， in comparison with the estimated rotor current obtained from the stator voltages and currents. A proportional-integral（PI） control adjusts the rotational rotor speed， driving the error between the measured and estimated currents to zero. A 50 kW DFIM prototype system is built to verify the theoretical analysis. Using estimated rotational speed and rotor position， both no-load variable speed tracking and decoupled active/reactive power control are achieved in experimental testing. The simulation and laboratory experimental results show the effectiveness of the proposed sensorless control scheme.