Abstract: Due to the accumulation of errors between processes during CNC machining, the accuracy of CNC machining is seriously affected. A new CCD visual inspection process is proposed to realize on-line inspection and error compensation of machining dynamic datum. The visual feature extraction method of dynamic datum is studied to obtain the processing datum position and error. The embedded control technology is used to realize the online acquisition and processing of visual images. The same as the ordinary tool of the visual diagnosis probe is installed in the CNC machining center tool magazine through the standard taper shank, through the CNC program code to achieve integrated control functions. For the verification of the key parts of the automobile, the inspection accuracy of the visual diagnosis probe reaches 0.03 mm, and the inspection efficiency is improved by 3 times compared with the CNC on-line inspection method based on the trigger type probe, which proves that the inspection process is accurate in inspection and efficiency. Both can meet the needs of automated inspection of production lines.