The dependence of fluorescence intensity on temperature change has made fluorescent microsphere temperature measurement a widely available technology. In this work, blue and orange polystyrene microspheres were introduced into sodium carboxymethyl cellulose (CMC-Na) hydrogel to successfully construct a dual-emission fluorescent material. This dual-phase material inherits the excellent optical properties of microspheres and the gel property of CMC-Na and shows long-term thermal and structural stability. Single-wavelength ultraviolet excitation (365 nm) shows that the emission peaks at 429 and 580 nm are different from the fluorescence quenching caused by temperature change, providing a ratio measurement method for temperature measurement. This material is then packaged with the tip of the quartz optical fiber to produce the fluorescence intensity ratio (FIR) optical fiber temperature sensor. The experimental results show that FIR has a linear relationship with temperature from 10 °C to 60 °C, and the sensitivity of temperature is 0.00466 $^{\circ }\text{C}^{-1}$ . In addition, the satisfactory reliability, stability, and timely response characteristics of the sensor prove that the proposed fluorescent material is an ideal choice for temperature sensing and has great application potential in this field.