Abstract: The phosphors LiY(MoO₄)₂:Yb³⁺/Er³⁺ with remarkable up-conversion emission character were synthesized by means of high-temperature solid state reaction method. Experiments were carried out to determine the crystal structure, up-conversion emission optical properties and temperature sensing of the phosphors. Under 980 nm laser, the LiY(MoO₄)₂:Yb³⁺/Er³⁺ exhibits an intensive green emission bands which can be assigned to ²H_11/2/⁴S_3/2→⁴I_15/2 transitions. The temperature sensing properties were studied by measuring the fluorescence intensity ratio of the ²H_11/2(1) and ⁴S_3/2(1) emitting energy levels in the temperature range from 298 to 513 K. The maximum relative sensitivity was 1.785% K^-1 at 298 K and the maximum absolute sensitivity reach to 263.20×10⁻⁴ K⁻¹ at 473 K, and the calculated energy gap ΔE between ²H_11/2(1) and ⁴S_3/2(1) levels was 756.71±27.48 cm⁻¹, suggesting that the present phosphor is a suitable candidate for optical temperature sensors.