Abstract: 3D LiDAR generates rich point cloud data by emitting laser beams and accurately measuring the return time of reflected light, obtaining the 3D coordinates of the module surface. This technology is efficient for size inspection of MiC (Modular Integrated Construction) modules, and can quickly determine whether the module contour meets the requirements of field and assembly accuracy. A 3D LiDAR is used to scan a modular building with a relatively regular appearance. Considering the huge amount of raw point cloud data, point cloud downsampling technology is utilized to perform lightweight processing on the data while retaining key features. Next, based on SCAN vs BIM technology, the processed point cloud is accurately matched with the constructed BIM model to accurately identify module manufacturing errors. The results show that compared to manual detection, this method only requires one person to operate on site, which can significantly improve the efficiency of module size inspection, reduce labor costs, and increase enterprise profits. The research results and engineering experience can provide ideas for MiC module size inspection and important references for virtual pre assembly technology.