The invention provides a radiation dosimeter, wherein the measuring instrument includes a built-in processor, and is respectively connected with the built-in processor to a wireless communication device, a display module and a power supply; the nuclear radiation detection device includes a connected NaI crystal probe, a photoelectric A multiplier tube, an amplifying circuit and a digital pulse amplitude analyzer, the pulse amplitude analyzer is connected to the built-in processor, the measuring instrument of the present invention has high sensitivity and good energy response characteristics, and can be used in medical treatment, and completion, nuclear submarines, nuclear power plants, etc. In areas with high radiation dose, at the same time, the measuring instrument is small in size, and the digital display of dose rate status is more intuitive.