Dihydroxyurea　(DHU)　is　a　new　salt-free　reducing　agent　applied　for　the　separation　of　Pu　and　Np　from　U　in　spent　fuel　reprocessing.　This　paper　reports　on　the　gamma-ray　radiolysis　of　DHU　in　HNO3　and　its　radiolytic　products.　DHU　is　relatively　stable　against　radiation　at　the　dose　supposed　to　be　absorbed　in　the　separation　of　Pu　and　Np　from　U.　The　main　radiolytic　products　are　H-2,　CO2,　N2O　and　NH4+.　The　volume　fraction　of　H-2　increases　with　the　dose,　but　decreases　with　increasing　HNO3　concentration.　The　quantity　of　CO2,　N2O　and　NH4+　increases　with　the　HNO3　concentration　and　the　dose.