The invention relates to a system and a method for detecting a single-phase ground fault point of a power distribution line. A switch, a sampling resistor, a current-limiting inductor and a processor which are connected in series with one another to form a zero sequence current loop form a circuit which is connected between a neutral point of a transformer and the ground, so that time constants at different inductance values can be obtained, and a group of time constant solution modes can be obtained according to a time constant formula; therefore, an inductance value of a cable from a bus to the single-phase ground fault point is calculated; the length of the cable is calculated according to a relation of the inductance value and the impedance and the length of the cable, namely the position of the single-phase ground fault point is determined; subsequent quick maintenance is facilitated; and the influence on a power grid can be reduced to the maximum extent.