The invention belongs to the technical field of nuclear radiation monitoring and protecting, and particularly relates to a post-accident high-range region radiation monitoring device. The monitoring device comprises a gamma-sensitive ionization chamber detecting device installed in a containment and a hard cable through-connection box connected with the gamma-sensitive ionization chamber detectingdevice through a hard cable. The monitoring device further comprises a front-end processing unit, which is arranged in a containment outer measurement compartment and connected with the hard cable through-connection box through a hard cable, and an in-situ radiation treatment unit arranged on a wall of the containment outer measurement compartment, and the in-situ radiation treatment unit is in communication with the front-end processing unit through a RS485 connector, and a junction box is connected with an ionization chamber detector and the in-situ radiation treatment unit separately, andprovides a power supply. A measurement range of the post-accident high-range region radiation monitoring device is 1*10<-2> Gy/h to 1*10<5> Gy/h, the measurement range is wild, the range width reaches8 orders of magnitudes, and an upper measurement limit reaches 105 Gy/h; and the post-accident high-range region radiation monitoring device resists accident conditions of irradiation, high temperature, high voltage, high humidity and the like.