High peak power and high beam quality laser is vitally valuable for applications in laser machining and other fields. A fiber laser with repetition frequency of 50 kHz, pulse width of 3.9 ps, and average power of 10.9 mW is used as the seed source. The average output power of 27.65 W is obtained in double-passing amplifier of two stages, with the pulse peak power of 65 MW. The first amplifier stage is end-pumped Nd∶YVO4 solid amplifier, and the second is side-pumped Nd∶YAG solid amplifier. The beam quality is preserved by a double-passing configuration for spherical-aberration compensation. By optimizing the beam filling factor in each solid amplifier, the M2 factor of the output beam reaches 1.30 finally.