Strata erosion is a widespread phenomenon in sedimentary basins. The generation, migration,and accumulation of hydrocarbon is influenced by the scale of erosion, so estimating the amount of erosion is essential in the analysis of oil and gas beating basins. According to the geological features in the Subci Basin and the actual data, using the integrated method, we estimated the level of erosion at the unconformities caused by the Sanduo event. By using the mudstone interval transit time method and the vitrinitc reflectance method on data from typical wells, it can be concluded that the Gaoyou, Jinhu,and Hongze depressions suffered strong strata erosion from the late Eocene to Oiigocenc, and the total strata erosion thickness was 300-1,100 m. Different tectonic units in the same depression have extremely uneven erosion intensity: the low convex regions have the maximum erosion thickness, amounting to 800-1,100 m; the slope regions have an erosion thickness of generally 600-800 m; the erosion thickness of the slope-hollow transition zone is 300-500 m. For the whole basin, we used the strata thickness trend analysis method combined with the interval transit time and vitrinite reflectance methods to estimate the erosion thickness in the Sanduo period. The results show that the most severe erosion of the Sanduo event in the Subei Basin is between 1,000 m to 1,200 m, mainly located in depressions around the Jianhu Uplift; the deep hollow area has the least erosion, generally about 300-600 m, and the erosion in the slope area is about 600-900 m. Compared with the north part, the south part has relatively little erosion. It is also proved that the Sanduo movement has heterogeneous intensity, and the west region has greater intensity than the east region.