An oscillator using the High Order Modes Lamb Wave (HOMLW) excited by Interdigital Transducers (IDT) is presented. A filter is inserted between the Lamb wave delay line and the amplifier in the feedback loop, which determines the operating mode of the Lamb wave. The phase velocity of the HOMLW is much higher than that of the SAW, which makes it easy to fabricate a high frequency oscillator. A HOLMW (a13 mode) with the phase velocity 19652m/s is obtained in experiments; the oscillating frequency is 5.30 times higher than that of the fundamental mode (a0 mode) excited by the same IDT. By increasing the oscillating frequency, the sensitivity of sensors using the oscillator can be greatly increased.