When the high resistance neutral point grounded system in wind farm occurs a single-phase fault, the conventional busbar differential protection has sensitivity problem. To avoid this situation, a high sensitivity differential protection based on the principle of waveform recognition is proposed, which identifies fault waveform characteristics, adjusts floating threshold according to real-time load and the differential ratio factor according to harmonic content of the system. The method can effectively avoid malfunction of high sensitivity differential protection caused by harmonic wave. RTDS simulation results show that this method can isolate fault quickly when a single-phase fault occurred in the high resistance neutral point grounded system. The application of the proposed method is of great significance to protecting electrical equipment and maintaining the stable operation of the wind system.