Abstract: In order to address the application issues of UAV nap-of-the-object photogrammetry in high-precision three-dimensional realistic modeling of hydraulic projects, taking the Xiluodu Hydropower Station as an example, this paper compares nap-of-the-object photogrammetry with oblique photogrammetry, and investigates the presentation effect and accuracy of the three-dimensional models obtained by the two methods on hydraulic structures. It was found that the pixel accuracy of oblique photogrammetry models was approximately 1 to 2 cm, while the pixel accuracy of nap-of-the-object photogrammetry models was around 3 mm. Nap-of-the-object photogrammetry three-dimensional models can significantly enhance the fineness of model textures and the accuracy of shape structures, but exhibit minor enhancement in length measurement accuracy.The research results can provide a reference for the application of UAV nap-of-the-object photogrammetry in hydraulic projects.