Abstract: A broad spectra detection system is developed, which includes the UV-ray imaging detector and X-ray imaging detector. By this system, the UV-ray and X-ray induced by dielectric breakdown which occures in vacuum under microwave field are diagnosed. The results show that the X-ray dose is 9.28×102～1.64×103 Gy in the environment and 5.38×102～1.09×103 Gy when dielectric breakdown occurs, as the operation parameters of HPM source is 100 Hz and 5 s. As the HPM pulses repetition frenquence and operation time increases, accordingly, the induced X-ray dose increases obviously. Furthermore, the UV-ray induced by HPM dielectric breakdown can be observed through this broad spectra detection system．