The invention discloses a power transmission line fault location method. The method comprises the following steps: carrying out first fault location by utilizing line positive-sequence parameters obtained before fault and first transient data of the line obtained after fault to obtain an initial fault location value; calculating line positive-sequence parameters obtained after fault by utilizing the initial location value and second transient data of the line obtained after fault; and carrying out fault location again by utilizing the line positive-sequence parameters obtained after fault and the first transient data to obtain a corrected fault location value. The line positive-sequence parameters obtained before fault and the first transient data of the line obtained after fault are utilized to carry out initial fault location; in order to improve fault location precision, the line positive-sequence parameters obtained after fault are calculated based on the initial fault location value; and then, fault location is carried out again by utilizing the line positive-sequence parameters obtained after fault, which is equivalent to an effect that the initial fault location value is subjected to correction processing, so that higher-precision fault location value can be obtained. Besides, the invention also discloses a power transmission line fault location system.