The invention discloses a judgment and locating method of an earth point of an extra-high-voltage long-distance power transmission line. The method comprises the steps that whether the power transmission line is normally connected is preliminarily judged by utilizing three-phase insulation resistance measurement values, and if yes, it is judged that the power transmission line has no earth point;if not, the next step is executed; when the power transmission line has no breaking point, it is judged that the power transmission line has an earth point, the phase line where the earth point of thepower transmission line is located is further determined by calculating the three-phase direct current resistance of the power transmission line, and is set as an earth fault phase line; the earth point is located, on-site line patrol is carried out on the power transmission line according to the locating results to remove the earth point; the steps above are repeated until all earth points are removed.