We demonstrate a femtosecond Ti: sapphire oscillator with ultralow repetition rate and ultrahigh peak power by inserting a specially designed Herriott telescope to increase the length of the cavity.By analyzing the intra-cavity dispersion and optimizing the extra-cavity compressor, stable pulses with repetition rate of 11 MHz and single pulse energy higher than 72nJ was obtained under 532 nm pump laser with average power of 8.2 W.The peak power of the pulses from the novel cavity is much higher than that from the original oscillators.