The big exit burr would be formed after the common drilling (CD) process of titanium alloys (Ti6Al4V) using a traditional twist drill,which would lead to the difficulty in deburring operations and has a negative influence on assembly quality of fastener.In this paper,a novel tool of 8-facet drill was introduced and the ultrasonic vibration drilling (UVD) technology was employed so as to perform the basic theory and experiment study of exit burr formation in ultrasonic vibration drilling titanium alloys using 8-facet drill.The exit burr formation process of CD and UVD as well as the exit burr reduction mechanism of UVD were analyzed by theoretical method, meanwhile the exit burr reduction effects of UVD were verified by experimental method.The results indicate that compared with the CD of Ti6Al4V,in the UVD process,the cutting ability of drill bit tool is greatly enhanced.The thrust force,cutting temperature and exit burr height decrease by 16% to 20%,18% to 21% and 82% to 89% respectively,as well as the trouble and cost of deburring operations in assembly process will be effectively reduced.