Ce³⁺-activated Gd₃(Al,Ga)₅O₁₂:Ce scintillation ceramics have been widely studied due to their excellent scintillation properties. However, the relatively long radiative lifetime and slow decay components limit their applications in X-ray imaging. To address these issues, Lu³⁺ ions were introduced to partially substitute Gd³⁺ ions, thereby weakening the role of self-trapped states in the excitation process of Ce³⁺ and reducing the negative effects caused by shallow electron traps. As a result, the scintillation decay time was, overall, shortened, and an average decay time of 63 ns was obtained when x = 0.997. Meanwhile, the afterglow behavior induced by shallow electron traps was significantly suppressed (for the sample with x = 0.5, the afterglow intensity was measured to be approximately 0.48% of the initial intensity at 100 ms after the X-ray excitation was turned off). Meanwhile, an X-ray imaging spatial resolution comparable to that of commercial CsI:Tl (10 lp mm⁻¹) was achieved for the (Gd,Lu)₃Ga₂Al₃O₁₂:Ce³⁺ scintillation ceramics.