Abstract: A new kind of realizable ultrasonic delay line is proposed for long time delay application,which is based on the conversion between Rayleigh waves and plate waves by shallow groove gratings on substrate surface.The experimental devices fabricated on YZ-LiNbO₃ have exhibited the ability to delay a narrow band signal for a delay time a couple of times longer than its Rayleigh wave counterpart.Because they are made with the same planar lithographic technology as that used in SAW devices,the new configuration retains advantages of reliability and reprodu-cibility.Approximate analysis for the device is provided for understanding its operation.