The invention discloses an extract method of high-impedance-grounded fault waveform distortion features, and belongs to the field of power system default detecting and protecting. According to the method, firstly, lowpass filtering is conducted on zero sequence current momentary value by a disperse three-time center B-spline function aiming at the zero sequence current momentary value of a to-be-detected feeder line, and then filtering is conducted on the sequence again after the lowpass filtering by a second derivative function of the disperse three-time center B-spline function, and finally, a coefficient of efficient characterization high-impedance-grounded fault features, namely, a zero sequence current zero crossing point distortion coefficient is obtained through calculation, and therefore whether a high-impedance-grounded fault is generated or not is judged through comparison of the zero sequence current zero crossing point distortion coefficient and threshold value. The extraction method is capable of improving detecting success rate of a high-impedance-grounded fault effectively, and damages caused by the high-impedance-grounded fault can be reduced.