A high-sensitivity temperature sensor based on optical fiber delay is proposed in this paper. The sensor system is designed and tested in a temperature range of 0°C to 100°C with increments of 5°C. The output delay difference is found to be linearly proportional to the temperature with an average fluctuation less than 0.1 ps. To achieve an overall low cost and practical detection, a simple detection system is developed to measure temperature, and a potential for high temperature sensitivity is shown by analyzing the system. As a result, this sensor system is proven to be feasible and practical, and temperature can be measured in a simple and economical way.