Inorganic phosphors with tunable broadband emission hold significant applications in solid-state lighting. Herein, a series of novel Sr3YGa2O7.5: Bi3+, Eu3+ (abbreviated as SYGO: Bi3+, Eu3+) phosphors with tunable optical properties were synthesized by high-temperature solid-state reaction process. The photoluminescence excitation (PLE) spectrum of Sr3YGa2O7.5: Bi3+ ranges from 200 to 400 nm with two peaks at 280 and 331 nm, matching well with the n-UV chip based white light-emitting diodes (WLED). Under ultraviolet light excitation, a single Bi3+-doped Sr3YGa2O7.5 phosphor exhibited five distinct luminescence peaks at 410, 510, 560, 605, and 700 nm at 10 K, which are attributed to the 3P1→1S0 transition emissions of Bi3+ ions occupying the four Sr sites and one Y site within the Sr3YGa2O7.5 host lattice. The optical tuning of the Sr3YGa2O7.5: Bi3+ phosphor is achieved by designing the Bi3+→Eu3+ energy transfer and changing the excitation wavelength based on the selected site occupation. The Commission Internationale de l'Eclairage (CIE) coordinates and emission color of the Sr3YGa2O7.5: Bi3+, Eu3+ phosphors were successfully tuned from blue via white to red. The energy transfer efficiency from Bi3+ to Eu3+ can reach as high as 89.54 %, and this energy transfer process is predominantly governed by the dipole-quadrupole interaction. In addition, the white LED device prepared by combination of SYGO: 0.02Bi3+, 0.03Eu3+ phosphors with 365 nm chip has high color rendering index (CRI) of 85.5 and low correlated color temperature of 3537 K. As the driving current increases, the white light emitting diodes (WLED) device demonstrates good color stability. Based on these findings, the synthesized SYGO: Bi3+, Eu3+ phosphors can serve as color-tunable and single-phase white phosphors with potential applications in UV-excited white LEDs. © 2025