Abstract: This paper presents a low insertion loss SLW filter on an optimum-cut orientation LiNbO₃ using new RMSC.The insertion loss have been reduced to 3 dB without external phase shift networks,and the out-of band rejection is up to 23 dB.The fractional bandwidth is up to 2-5%.The out-of band rejection can be reduced to 40 dB when two IDT are apodized.