A diffusion bonding method of quasi-phase-matched (QPM)-GaAs crystal preparation is studied. By ultra-high vacuum pre-bonding-high temperature annealing method, the preparation of three quasi-phase-matched crystals is completed under different load pressures. The polarization period length of the QPM structure is 219 μm, number of layers is 44, the diameter is 18 mm, and the effective aperture is 15 mm. The best transmittance of the foundation and frequency doubling is above 30% without anti-reflection coating. Using transversely excited atmospheric pressure (TEA)-CO2 laser with 90 ns wide main pulse and 2~6 μs wide tailing as foundation source, we acquire second harmonic generaction (SHG) output with efficiency more than 4% on 4.63~5.37 μm waveband by tuning foundation wavelength. When the foundation wavelength is 10.68 μm, main pulse energy is 409 mJ, the density in QPM-GaAs is 3.65 MW/cm2, we get SHG output with 26.9 mJ pulse energy, 298 kW peak power, and the SHG efficiency of 6.58%.