The invention discloses an unmanned plane aerial photography image calibration method suitable for slope measurement. According to the method, firstly, an image calibration model is established; secondly, points are vertically acquired by an unmanned plane, slope map image data and calibration data are acquired, and a slope angle Slope and a slope image azimuth Azimuth are acquired through calculation according to the acquired data; whether a distance measurement module is available is determined, if yes, the distance measurement module is employed to measure the vertical distance Length; if not, calibration points are acquired to replace the vertical distance Length; according to the acquired vertical distance Length, a slope image scale SlopeScale, a geographic three-dimensional coordinate of an image origin Origin and a geographic three-dimensional coordinate of a target point are calculated, and calibration is accomplished. The method is advantaged in that the unmanned plane measurement calibration technology is made not to be limited to the plane, scientific basis is further provided for slope measurement and projection measurement demands, effective guarantee is provided foraccurate measurement, rapid and easy calibration is realized, and slope image calibration accuracy and calibration efficiency are improved.