Abstract: In order to produce the Al-based amorphous powder that could meet the requirement for 3D printing, the Al ₈₆Ni ₇Er ₅Co ₁La ₁ alloy powder was prepared by gas atomization. The effect of the gas atomization parameters on the particle size were analyzed though adjusting the superheat, gas pressure, and diameter of the tube. The size distribution, phase composition, surface morphology, micro-structure and thermal stability of the alloy powder were detected through laser particle analyzer, X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC). It indicates that the particle size of the alloy powder decreases with the increase of gas pressure, decrease of the diameter of tube and increase of the superheat. The highest fine powder rate was obtained when the gas parameter was as the followings, overheat 100℃, gas pressure 9MPa, diameter of tube 3mm, the mass fraction of the powder with particle size of less than 75μm could be above 70%. With the decrease of the particle size of the powder, the structure of the powder transformed as the followings, fcc-Al + Al ₁₇Er ₂ + unknown phase → amorphous + fcc-Al + Al ₁₇Er ₂ + unknown phase → fcc-Al +amorphous→ amorphous, the powder with size of less than 20μm was all amorphous state.