How to improve the efficiency of the linear ultrasonic motor with hard contact materials (HLUSM ) or the precision motion stage driven by HLUSM ,becomes a hot issue .Analysis and testing of friction behavior on the contact interface of HLUSM is one of the key issues .Under the action of ultrasonic vibration and impact ,the fric-tion behavior on contact interface is very complex due to micro-amplitude and high frequency .Moreover ,it is diffi-cult to observe and test it .Focusing on the frictional behavior on the interface of HLUSM ,a new method ,through testing the vibration of the driving tips (scanning vibrometer PSV-400-3D) and the motion of the slider (displace-ment sensor LK-G30) ,respectively ,is proposed .Then ,take the HLUSM as an example ,theoretical analyses and experiments are carried out .Theoretical analysis shows that the average speed of the slider should be 600 mm/s when there is no slippage between the stator and slider during the contact process .Experimental results show that the average speed of the slider is about 390 mm/s .At the same time ,the tangential vibration speed of the driving tip of HLUSM is larger than 600 mm/s .Therefore ,there must be slippage between the stator and slider of HLUSM .Further experimental results show that the maximum efficiency is less than 10% .The slippage on the contact interface should be the main reason for the low efficiency of HLUSM .