Abstract: The procedure of image preprocessing, segmentation and feature calculation is studied and the image processing system for the measurement of lubricant wearproof property is developed based on the characteristics of the micro-image of steelball wear spots. Least error method is adopted to obtain the threshold and segment the image. At the same time, combining the shape factor of wear spots, those not belonging to wear spots are eliminated, so the recognition of the image after segmentation is realized. Experimentalresults show that the measurement accuracy and automation degree are improved using computers to acquire and process image automatically.