Abstract: This paper presented an optimal design on surface acoustic wave (SAW) reflective delay line using coupling of modes (COM) and equivalent circuit model,the reflective coefficient S₁₁ of the SAW device was deduced to evaluate the device performance.Typical SAW reflective delay line consists of a piezoelectric substrate,an interdigital tranducer (IDT) and several reflectors positioned along the acoustic propagation direction.The effects of the design parameters of the device as structure of the IDT and reflector types on device performance were investigated,and the optimal design parameters were determined.Based on these parameters,a 440 MHz SAW reflective delay line with single phase unidirectional transducers (SPUDT) and three shorted grating reflectors was fabricated on 41°YX LiNbO₃,and the measured S₁₁ agrees well with the simulated one,sharp reflection peaks,high signal noise ratio (SNR),and low spurious noise between the reflection peaks were observed.