Abstract: Aim To solve the problem of tool breakage monitoring's poor prac ticability and low reliability during automatic manufacturing process. Methods According to the feature of tool breakage's acoustic emission signal, the distinguish ing method with double threshold values was realized hardware circuit and the special method of interference resistance was adopted. The monitoring system was installed without any effect on the normal manufacturing process. Results The correspond ing monitor was developed. The working principle and structure of the monitor was discussed. Conclusion It has been proved by the experiments that this system has fair practicability and interference resistance.