The utility model relates to an ultraviolet sensor with a thermostat. The ultraviolet sensor comprises a casing and a photoelectric sensor. The thermostat is installed in the casing, the photoelectric sensor is installed in the casing through the thermostat, and the thermostat collects the work temperature of the photoelectric sensor in the casing, compares the collected work temperature with the preset temperature and enables the photoelectric sensor to work within the range of the preset temperature. According to the ultraviolet sensor with the thermostat, the adverse influence of the temperature characteristic of the photoelectric sensor on the radiation measurement is radically eliminated, the measurement accuracy of the ultraviolet radiation sensor is greatly increased, and the actual requirements of all-region, high-accuracy and perennial outdoor ultraviolet radiation monitoring are met; by means of an overall structure design scheme that one end of a heat insulation barrel is used for enhancing heat insulation effect to reduce the heat flow diffusion rate of constant temperature points, and the other end of the heat insulation barrel is used for enhancing radiating performances to decrease the continuous increasing trend of the temperature difference of cold and hot ends, the temperature control performance is strengthened, and the power consumption of the constant temperature control is reduced; and the structure is compact.