Abstract: Aiming at the fracture of titanium alloy Ti6Al4V screw in the assembly process, chemical composition analysis, fracture analysis, surface morphology observation and microstructure analysis are carried out by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy and metallographic examination. The results show that the chemical compositions of the screw meet the requirements, that the brittle crack comes first to the screw and then the ductile fracture, and that the screw thread surface has defects such as pitting, notch and scar. From the comprehensive analysis results, it can be seen that during the roll forming process, due to the poor lubrication of the abrasive and material, the screw and the mould adhere, so the pitting, notch and scar are formed on the thread. There is stress concentration appears in a serious scar formed on the surface of the root during the loading process, which becomes a crack source and then fractures.