Eu3+-doped LiY(PO3)4(1-x)(SO4)4x (LYSO:Eu) phosphors are synthesized by high-temperature solid-phase method and the crystal structure, microscopic morphology, and photo-spectrographic characteristics are analyzed. The phosphor exhibits the strongest excitation peak at 397 nm, which indicates that the sample can be effectively excited by the near-ultraviolet/ultraviolet LED chip. The characteristic emission peaks of Eu3+ ion 5D0→7FJ (J = 1 ~ 4) are observed from the PL spectrum, and the orange emission peak originating from the magnetic dipole transition 5D0→7F1 of Eu3+ is located near 597 nm. When the SO42- concentration exceeds 22.5 mol%, the quenching of the phosphor occurs. The Eu3+ emission still retains 78.8% of the initial strength at 495 K, with excellent thermal stability. The emission intensity is decreased with the increase of SO42- concentration, indicating that the SO42- co-doping led to an increase in the probability of non-radiative transitions. The best quantum efficiency of the LiY0.95(PO3)2.6(SO4)1.4: 0.05Eu3+ sample is 86.65%, and the CIE chromaticity coordinates of this sample are (0.653, 0.347), which are close to the international standard red color coordinates (0.67, 0.33). These results indicate that LYSO:Eu has a good application prospect in NUV/UV excited white LEDs. Influence of anionic substitutions of SO42- to the optical properties is discussed.