Objective According to industrial inspection speed and accuracy requirements of groove width detection of cartridge, traditional manual measurement does not meet the needs of automatic production. Methods An Image Collection System was constructed using CCD camera of DH-SV1410 and LED source, meanwhile a measurement system was compiled by C^# on VS2010 platform based on machine vision. The method of sub-pixel edge contour extraction was used to exact the location of groove edge and a groove width detection method of cartridge was designed. Results Comparative experiments on the same part of one cartridge and multiple cartridges showed that the system had micron error, with a maximum error of less than 2 micron. Conclusion The detection accuracy of the system in groove width of cartridge could achieve 10 micron order, which meets the requirement of online measurement of cartridge, and the measurement results were not influenced by subjective factors, with very high efficiency.