A Yb-doped picosecond fiber laser with 35.4W for average power, 12ps for pulse duration, and 300kHz~1MHz for repetition rate is designed based on cascade amplification. The oscillator and the pre-amplification system are comprized of all fiber. Rod-type photonic crystal fiber is used as the gain medium of the main amplifier. The output repetition rate can be adjust from 300kHz to 1MHz by an Acousto-Optic Modulator (AOM). The all-fiber design of the oscillator and the pre-amplifiers has the characteristics of simple optical path structure and high environmental stability, which is expected to promote the industrialization process of high-energy femtosecond fiber laser and improve its adaptability under complex environment.