Al0.1Ga0.9N/GaN heterostructure front illuminated visibleblind UV photodetectors were fabricated,The diodes were irradiated with 0.8 MeV electrons at fluences of 5×1013, 5×1014 and 5×1015 n/cm-2 in turn. I-V characterization and response spectrum of the detectors were measured before and after irradiation to analyze the irradiation effect. After higher electron fluence of irradiation, the reverse leakage current is enlarged with one order. Then the SiN/nGaN metal insulator semiconductor diodes were fabricated to study the effect on the electrical properties of SiN/nGaN interface. The results showed that the electron irradiation induces new interface density between the SiN and GaN. The response spectrum after irradiation is slightly smaller than before irradiation which shows the radiation hardness of the AlGaN photodetector.