[en] Well-crystallized NaYb(MoO₄)₂ doped with lanthanide ions (Ln³⁺: Er³⁺, Tm³⁺ and Ho³⁺) are successfully synthesized by hydrothermal method with further calcination. And the samples with different morphologies are obtained by changing the pH values and the molar ratio of Ln(NO₃)₃/Na₂MoO₄ of the resultant solutions. The upconversion (UC) luminescence spectra of NaYb(MoO₄)₂: Ln³⁺ between 323 K and 573 K under 980 nm excitation exhibit temperature-dependent property. The fluorescence intensity ratio (FIR) techniques with thermally coupled states (TCS) (Er³⁺: ²H_11/2, ⁴S_3/2 → ⁴I_15/2, Tm³⁺: ¹G_4(1),(2) → ³H₆, Ho³⁺: ⁵F_5(1),(2) → ⁵I₈) have high sensitivity (S) values (Er³⁺: 0.0122 K⁻¹ at 548 K, Tm³⁺: 0.0025 K⁻¹ at 323 K and Ho³⁺: 0.00035 K⁻¹ at 323 K). The non-TCS (Ho³⁺: ⁵F₅, ⁵S₂/⁵F₄ → ⁵I₈) is used to extend the range of S, and the slope of FIR (non-TCS)-T is the S value as high as 0.02455 K^-1 in the wide temperature range from 323 K to 573 K. - Highlights: • Er³⁺/Tm³⁺/Ho³⁺ doped NaYb(MoO₄)₂ phosphors show strong visible luminescence. • FIR technique of thermally coupled states (TCS) and non-TCS have been explained. • The temperature sensor has high sensitivity in wide range (323–573 K).