The blue oil fitting quality of the shim block is closely related to the stability of the equipment such as the ship's main engine. The blue oil fitting quality should be inspected during the equipment assembly to ensure that the assembly process meets the technological requirements. The machine vision method is used to detect the blue oil fitting quality of the ship's shim block. The images of the blue oil fitting are obtained and cropped, then processed and calculated based on the OpenCV framework, and the proportion of the blue oil enamel in each part is marked, which realizes the rapid detection of the blue oil fitting quality.