The invention provides a line temporary grounding quantity determination and high-precision positioning method based on double-end measurement. The method comprises the steps that S1, the tail end ofa power transmission line is suspended in midair and not grounded, the insulation resistance over the ground of the line is measured at the head end of the power transmission line by adopting an insulation resistance measuring instrument, and when the line insulation resistance is greater than 100-megohm, the line has no grounding point; and when the line insulation resistance is 0-100-ohm, thereis a temporary grounding point in the middle of the line; and S2, when there is the temporary grounding point on the line, the distance upper limits of the grounding points on the line from the head end and the tail end are determined by adopting a positioning method of the head end and the tail end; if the distance upper limits of the grounding points on the line from the head end and the tail end are crossed, it is judged that only one grounding point exists on the line, and then accurate positioning of the grounding point position is carried out by adopting a double-end high-precision positioning method; and otherwise, it is judged that two or more grounding points exist on the line, and the double-end positioning method is adopted to preliminarily define the grounding point range. Themethod has the characteristics of resisting power frequency interference, high positioning precision, simple and feasible measuring method and the like.