Ce:GAGG scintillation crystals with different sizes and thicknesses (2, 4, 6, 8, 10 mm) are selected to analyze the influence of self absorption on Ce: GAGG scintillation crystals by measuring the transmittance. At the same time, the effects of different surface roughness, package and coupling mode on light output and energy resolution of Ce: GAGG scintillation crystals are investigated. The experimental results show that the optical output and energy resolution of Ce: GAGG scintillation crystal samples can be greatly improved by optimizing the surface roughness, encapsulation reflector and coupling mode. The best energy resolution of Ce: GAGG scintillation crystals is 7.0% by using 137Cs standard radioactive source.