In　this　study,　the　effects　of　1　MeV　electron　radiation　on　the　D-mode　GaN-based　high　electron　mobility　transistors　(HEMTs)　were　investigated　after　different　radiation　doses.　The　changes　in　electrical　properties　of　the　device　were　obtained,　and　the　related　physical　mechanisms　were　analyzed.　It　indicated　that　under　the　radiation　dose　of　5　x　1014　cm-2,　the　channel　current　cannot　be　completely　pinched　off　even　if　the　negative　gate　voltage　was　lower　than　the　threshold　voltage,　and　the　gate　leakage　current　increased　significantly.　The　emission　microscopy　and　scanning　electron　microscopy　were　used　to　determine　the　damage　location.　Besides,　the　radiation　dose　was　adjusted　ranging　from　5　x　1012　to　1　x　1014　cm-2,　and　we　noticed　that　the　drain-source　current　increased　and　the　threshold　voltage　presented　slightly　negative　shift.　By　calculations,　it　suggested　that　the　carrier　density　and　electron　mobility　gradually　increased.　It　provided　a　reference　for　the　development　of　device　radiation　reinforcement　technology.