The present disclosure provides a method for increasing luminescence uniformity and reducing afterglow of a Ce-doped gadolinium-aluminum-gallium garnet structure scintillation crystal, a crystal material and a detector. Sc ions are doped into the crystal material, and the Sc ions occupy at least an octahedral site. The effective segregation coefficient of active Ce ions is increased by a radius compensation effect of Sc—Ce ions and adjustment of lattice parameters, thereby the luminescence uniformity of the crystal is increased and the energy resolution is optimized; and at the same time, the potential barrier for Gd ions entering the octahedral site is increased, thereby the probability of the Gd ions entering the octahedral site is reduced, the density of point defects in the crystal is decreased, and the afterglow intensity is reduced. A general formula of the Ce-doped gadolinium-aluminum-gallium garnet structure scintillation crystal is {Gd1-x-y-pScxCeyMep}3[Al1-q]5O12, 0