The invention discloses a high-voltage power transmission line electric leakage detector which comprises a box body, a box door is arranged on the box body, a folding rod is arranged between the box door and the box body, an analysis processing module, a wireless receiving and transmitting module and a power supply module are arranged in the box body, and the high-voltage power transmission line electric leakage detector further comprises a walking mechanism and a clamping part. The two walking mechanisms are arranged on the portions, on the two sides of the box door, of the box body respectively, the clamping part comprises two detection clamps of an arc-shaped structure, and the inner sides of the detection clamps are provided with arc-shaped magnetic assemblies and guide mechanisms. According to the invention, the detection clamp is arranged, the magnetic assembly is arranged on the inner side of the detection clamp, the magnetic assembly is formed by sequentially splicing a plurality of magnetic blocks, and two adjacent magnetic blocks can rotate, so that the magnetic assembly can be bent, and the magnetic assembly is moved through the guide mechanism, so that the inner diameter size of a circular structure formed by the magnetic assembly is changed; therefore, the detector is provided with the adjustable magnetic assembly, so that the detector can detect different numbers of lines.