In order to quickly inspect hole position and normal vector of mounting holes on aircraft part, an onmachine inspection system based on machine vision was developed in this paper. The developed visual device, mounted to machine tool spindle, acquired image of mounting hole and laser spots along measuring path. The kinematic model for hole inspection was established. And method for calibration of system parameter was proposed, too. Special image processing method was designed for calculation of 2D coordinate of mounting hole position and laser spot. The verification experiment was carried out on test piece, and the result shows that the inspection accuracy of hole position and normal vector on aircraft part can reach 0.05 mm and 0.5° respectively, and the system can measure 15 holes per minute, which realizes the effective on-machine inspection of mounting holes on aircraft part.