The inhibiting effects of electrical treeing and insulation properties of LDPE contained with treeing inhibitors was studied under radiation environment. Barbituric acid and its derivatives were selected as treeing inhibitors. The inception voltage and growth of tree, AC breakdown strength, volume resistivity, high frequency capacitance, and dissipation factor were observed as a function of dose(up to 1000 kGy). And also, measurements of thermo-luminescence(TL), and gel content were carried out. Crosslinked low density polyethylene(XLPE) contained with treeing inhibitors shows better insulation characteristics such as electrical tree propagation, AC breakdown strength, and volume resistivity than those of pure LDPE. The most effective treeing inhibitor was found on the barbituric acid contained XLPE.