The Cu/15°YX-LiNbO3 surface acoustic wave(SAW) resonator is a key element of the wide band SAW filter, The existence of spurious transverse modes of the resonator will greatly deteriorate the passband performance of the SAW filter,which will cause the passband ripples and increase the insert losses, so as to reduce the signal-to-noise ratio of the system and cause signal misreading, The transverse modes suppression of the Cu/15°YX-LiNbO3 SAW resonator with the Piston technique was studied in this paper, The end size of the finger was optimized by the finite element method, The simulated results show that the spurious transverse modes around the main mode can be completely suppressed when the duty ratio and the length of the slow region are 0, 692 and 0, 65λ, respectively, The effectiveness of the simulation was verified experimentally, This offers a foundation for the application of the Piston technique to the transverse modes suppression of the wide band SAW filter with a structure of Cu/15°YX-LiNbO3,