The invention discloses a fiber high-temperature sensor based on a Nd:YAG transparent ceramic wafer and belongs to the technical field of optical fiber sensing. The sensor comprises a light source module, a fiber sensing probe module, a spectrum analysis module and a connection module. The fiber sensing probe module comprises a conical temperature sensing cap, the Nd:YAG transparent ceramic waferand a temperature sensing substrate. The front and back end surfaces of the Nd:YAG transparent ceramic wafer are used as reflection surfaces to carry out multiple interferences and then the reverse transmission is carried out, a temperature change causes the changes of a thermal expansion coefficient and a thermo-optic coefficient of the Nd:YAG transparent ceramic wafer, and the temperature measurement can be achieved by monitoring the drift of an interference wavelength. According to the fiber high-temperature sensor, a non-gelatinized package is adopted for an optical fiber sensing probe module, the problem of aging in a high temperature is effectively prevented, at the same time, a heat dissipation structure is added, the service life of a single-mode optical fiber in a high-temperatureenvironment is enhanced, and the fiber high-temperature sensor has the advantages of high practicability, low cost and a compact structure, and the measurement of 1000 degrees can be achieved.