Abstract: In a purified terephthalic acid(PTA) production device,some titanium alloy threaded studs connecting stirring shaft broke,and the fracture causes were analyzed by means of macroscopic and microscopic rupture surface analysis,mechanical property testing and microstructure observation.The results show that because of bearing eccentric wear,great fatigue load was applied to these studs with large differences in strength,so some studs exhibited fatigue cracking and when the remaining bolts could not support the working load,overload fracture happened.