The invention discloses a detector device for radiation monitoring, which comprises an ionization chamber part comprising a shell and an electrode part, a circuit part processing electric signals from the electrode part, and a metal seal box, wherein the circuit part is arranged in the metal seal box. Besides, a spherical gas filled ionization chamber, a signal amplification/data processing circuit, the metal seal box and other parts are all arranged in an insulating cover so as to further improve the adaptivity of the whole detector device to severe environment. Moreover, the outer layer of the insulating cover is plated with a conductive film, thereby achieving the electromagnetic shielding effect, improving the electromagnetic interference resistance of the signal amplification/data processing circuit, ensuring the stable performance and improving the measuring accuracy.