Slope failures and landslides associated with earthquakes and typhoons are major natural hazards in Taiwan's mountain highways. This paper attempts to apply photogrammetry technique to carry out speedy in-situ survey. We firstly create the three-dimensional (3D) model of a brick wall and validate that the average error is 0.28 mm in the measured distance. Afterward, the same measurement procedures are applied in an in-situ mudstone slope. The average error in the estimated distance is 0.41cm. Therefore, the investigating result guarantees the accuracy of applying Photogrammetry to investigate the geometry of in-situ failed slope.