Abstract: The fretting fatigue crack detection system was developed.In the system,the areas where the fretting fatigue cracks would happen were predicted at first,the strain gauges were used to collect the strain signals around those areas.The signals were transmitted to the computer after A/D converters.Then the data could be analyzed to acquire the accurate time of the initiation of fretting fatigue crack,and observe the crack’s expanding process.The result of fretting fatigue experiment shows that the fretting fatigue crack detection system is easy to use and accurate to find out fatiguecrack.The system solves the problems during fatigue experiment,such as hard to observe the crack,difficult to get the right time that the crack happens,etc.