Optical fiber sensors have the advantages of small size, low cost, high resolution, compact structure, strong anti-electromagnetic interference ability, etc., which have been widely used in structural health monitoring. The application of optical fiber high temperature strain sensors in the high temperature and harsh environment in aerospace, petroleum exploration, industrial smelting and other fields has attracted more and more interest of researchers. At present, thermocouples and resistance strain gauges are commonly used to measure temperature and strain, respectively. However, both of them have many shortcomings. Thermocouples are very expensive, low precision and sensitive to pollution; the resistance strain gauges themselves have very high costs, short service life, complicated pasting process and low measurement accuracy. Therefore, there are so many challenges for high temperature strain sensors based on electrical type in high-temperature and harsh environments and it is urgently ask for developing other kinds of sensors to be used in these environments. Optical fiber high temperature strain sensors are one of the most important sensors due to their many advantages. For example, they can be protected by ultra-high temperature ceramics, carbon/silicon carbide and other materials with mature preparation technologies, and can be used for thermal structure health monitoring in high temperature environment.It is of great significance to explore and develop optical fiber sensors that can be used in high temperature environment. However, when optical fiber high-temperature strain sensor is used to monitor the temperature and strain of thermal structure in the high-temperature environment in real time, the sensor can respond to temperature and strain at the same time in the demodulation process, resulting in the problem of cross-sensitivity. In the process of strain measurement, temperature affects the measurement results at the same time, resulting in a large strain measurement error. How to solve this problem is particularly important. At present, there are two demodulation methods: dual-wavelength demodulation and temperature compensation demodulation.Dual-wavelength demodulation method adopts dual-parameter matrix to demodulate temperature and strain, which can cause large measurement error in high temperature environment. In the temperature compensation demodulation method, one of the sensor structures is protected by adhesive package, so that it only responds to temperature, and the other sensor structure is compensated for temperature. However, this method is only suitable for the experimental test in low temperature environment because the adhesive is not resistant to high temperature. At present, the research scheme and technical route to effectively solve the temperature-strain cross-sensitivity problem of optical fiber sensors are not clear, especially for strain monitoring at ultra-high temperature. Therefore, it is an extremely urgent problem to design the sensor structure and improve the demodulation method to realize the accurate measurement of temperature and strain in high temperature environment. The developed optical fiber high temperature strain sensors should not only have a more reliable demodulation method, but also largely solve the main technical problems left by the current optical fiber high-temperature strain sensor.In this paper, sensing mechanisms, experimental methods and packaging applications based on FBG and optical fiber interference type high-temperature strain sensors are reviewed. The response characteristics of different sensing mechanisms to temperatures and strain are summarized and the measurement parameters of various fiber optic high temperature strain sensors are compared in table, including the measure range of temperature and strain, the sensitivity of temperature and strain, and the latest development of optical fiber high temperature strain sensor is introduced emphatically. Finally, the perspective of optical fiber high temperature strain sensor is forecasted.