The design of thermal interference connection between tool and ultrasonic horn was carried out,and the modification design of the connection parts were studied.According to the interference fit theory,the fit tolerance and assembly heating temperature of the tool and ultrasonic horn were designed.The modification model was established by using full arc bus modification and logarithmic bus modification,the stress distribution law of two kinds of modification methods and their combination modification were studied respectively.The results show that good shape modification results can be achieved through the outer circular surface of the tool and the inner hole of the horn modified by full arc generatrix with the modification amount of 8 μm and 10 μm respectively,or logarithmic generatrix with the load correction factor m is 0.2.The combination of logarithmic generatrix with load correction factor m is 0.2 and full arc generatrix with modification amount is 6 μm can realize the thermal interference connection between the tool and horn with a longer effective contact length and without stress concentration,so the modification effect is the best.