The invention discloses a contour line mapping and high-resistance region identifying method of transient electromagnetic detection data. The method comprises steps of inverting induced electromotive force data in different periods and different measurement points into apparent resistivity of spatial dispersion; using irregular triangular network to draw a contour line and establishing a single contour line collection array and a color array of a storage color value corresponding to the single contour line collection array; and at last, filling colors via apparent resistivity comparison and color searching method. Thus, precision and speed of contour line drawing of the transient electromagnetic detection data are improved; and during a color filling process, according to the set high-resistance region apparent resistivity lower limit and a corresponding assigned color value, all regions whose apparent resistivity values are larger than or equal to the high-resistance region apparent resistivity lower limit are provided with the assigned color value. In this way, a simple method is provided for rapid identification of a high resistance region and for some high resistance regions like a cavity region according to the range of the apparent resistivity.