Sulfur element doped RbNa3(Li12Si4O16-ySy):Eu2+ narrow-band blue emitting UCr4C4 phosphors were synthesized by a conventional high-temperature solid-state method. The zero-thermal-quenching performance for the UCr4C4 structure was obtained, i.e., the integrated emission intensity at 250 ℃ increases to 107% rather than that at room temperature. The sites occupation of Eu2+ ions and defect analysis reveal the corresponding luminescence adjustment and zero-thermal-quenching mechanism. Also, the cationic substitution strategy of Ti4+ for Si4+ is designed eliminate the shoulder band peak located at 525 nm for RbNa3(Li12Si4O16-ySy):Eu2+phosphors, and the color purityofblue eto mission is improved from 61.1% to 83.7%. It is indicated that the as-prepared RbNa3(Li12Si3TiO16-ySy):Eu2+ phosphors could be used as a blue-emitting candidate material for liquid crystal display backlighting. This work can provide a guidance for the design of UCr4C4 phosphors to achieve the zero-thermal-quenching performance and high color purity.