<p>To maximize the effective afterglow time of Zn₂GeO₄: Mn²⁺, Pr³⁺ phosphors, a second general rotational composite design strategy was employed to optimize the concentrations of Mn²⁺ and Pr³⁺. A quadratic regression equation model was established between the doping concentration of rare-earth ions Mn²⁺ and Pr³⁺ and the effective afterglow time. The theoretical optimal value of the effective afterglow time was precisely solved through a genetic algorithm. Using the high-temperature solid-state method, we successfully synthesized the phosphor Zn₂GeO₄: 0.5&#xa0;mol% Mn²⁺, 2.3&#xa0;mol% Pr³⁺ with the optimal doping concentration and performed detailed characterization and analysis. The results show that doping with Mn²⁺ and Pr³⁺ significantly improved the long afterglow properties of Zn₂GeO₄. Under 328&#xa0;nm excitation, a characteristic emission peak at 535&#xa0;nm was observed, and Zn₂GeO₄: Mn²⁺/Pr³⁺ exhibited an emission band corresponding to the ⁴T₁ → ⁶A₁ transition of Mn²⁺. In the Zn₂GeO₄: Mn²⁺/Pr³⁺ phosphor, Pr³⁺ substitution of Zn²⁺ generated positive defects of Pr^′_Zn and vacancy defects of V^′′_Zn. Furthermore, we measured the thermoluminescent properties of the optimal phosphor, calculating the trap depth to be 0.4608&#xa0;eV, and discussed the relevant characteristics of long afterglow luminescence.</p>