Ultrasonic motor （USM） utilizes a frictional force generated by ultrasonic vibration to realize rotary or linear driving. However， the ultrasonic vibration can not only produce a frictional force but also lead to the occurrence of the antifriction phenomenon. In this study， a detailed automatic dynamic incremental nonlinear analysis （ADINA） simulation research on USM's antifriction phenomenon is proposed， as well as the equivalent friction coefficients. To measure the antifriction effect， the transient-state equivalent friction coefficients of USMs are studied respectively under the standing wave and traveling wave excitation. Meanwhile， during the simulation research， the steady-state equivalent friction coefficients under different preloads， excitation frequencies and voltages are obtained. When the preload is small， the antifriction effect under the standing wave excitation is stronger than that under the traveling wave excitation. However， when the preload is large， the ultrasonic vibration is suppressed， the antifriction effects of the two excitation modes are therefore almost the same. In general， as the excitation frequency is close to the resonant frequency， the preload becomes smaller. Meanwhile， the larger the driving voltage is， the more significant the antifriction effect is. Among them， the influence of excitation frequency and preload is greater. This paper provides a useful method for the research and application of USM's ultrasonic antifriction.