The invention discloses a power frequency electrical parameter extraction method and system and a computer readable storage medium. The power frequency electrical parameter extraction method comprisesthe following steps of acquiring phase information of a three-phase voltage signal, a three-phase current signal and a three-phase voltage on a natural coordinate system of an ultrahigh-voltage DC inversion end AC line at commutation failure moment; converting the three-phase voltage signal and the three-phase current signal on the natural coordinate system to a dq0 coordinate system by a synchronous rotation coordination change method so as to obtain a voltage component and a current component corresponding to each phase on a d axis and a q axis; and obtaining a DC component corresponding toeach phase on the d axis and the q axis, and calculating an apparent power, an active power and a reactive power corresponding to each phase according to the DC component corresponding to each phaseon the d axis and the q axis. By the method, a power frequency component is conveniently and rapidly extracted when commutation is in failure.