Abstract: To address the problems of low operational efficiency, insufficient accuracy, and weak adaptability to complex terrain in traditional earthwork volume measurement methods, this paper takes a certain detention center project as a research case for in-depth exploration. In this project, based on oblique photography technology, unmanned aerial vehicles (UAVs) were used to quickly collect site image measurement data. It was calculated that the UAV completed data collection in a complex terrain area of 95,000 square meters in just 1.4 hours, significantly improving efficiency compared to traditional methods. Based on the collected data, a digital elevation model (DEM) was successfully created. At the same time, a BIM model was constructed using Revit, and the two were organically combined for earthwork volume calculation. The calculation results of this method were compared with the Southern CASS grid method. The results showed that the earthwork volume calculated from the original terrain model created using the site image measurement data obtained through oblique photography technology and the BIM design model had an accuracy error of less than ±2%, which was far lower than the error range of the traditional Southern CASS grid method. This provides a more accurate and reasonable analysis basis for earthwork balance schemes and effectively helps projects reduce costs and increase benefits.