Fluorescent optical fiber temperature sensor uses the long-distance transmission of optical fiber technology to avoid the harsh temperature measurement environment compared with the traditional active temperature measurement equipment in contact measurement. Aiming at the disadvantage that the traditional single channel circuit readout structure is vulnerable to external interference, a two-channel small and practical fluorescent temperature measuring device is realized. The whole system is divided into three parts:optical circuit design, circuit design and program design. The idea of two channel differential subtraction is adopted to completely eliminate the DC component and basically do not contain random noise, so as to obtain a single smooth fluorescence attenuation signal. And through the calibration experiment, the functional relationship between the fluorescence lifetime and the temperature is obtained. The experimental results show that the standard temperature deviation is 0.5 °C within the temperature range of 10 °C to 130 °C, basically meeting the temperature measurement requirements in some harsh environments such as high pressure corrosion and microwave medical.