A noncontact temperature measurement technique based on fluorescence variation was used to depict the temperature-dependent evolution of phase transition of a ferroelectric material, that is, Nd3+-doped (K0.5Na0.5)NbO3 ceramics. The slope of the fluorescence intensity curve changes dramatically in the two temperature regions of 450-475 K and 650-675 K, which correspond to orthorhombic-tetragonal and tetragonal-cubic transitions as confirmed by the temperature dependence of dielectric constant. Furthermore, the small deviations in delta TO-T and delta T-c indicate the good accuracy of this noncontact method. This work can guide other ergodic ferroelectrics to describe phase experience by the noncontact fluorescence method.