The invention discloses an XLPE cable insulation aging state determining method. The method includes firstly, determining whether aging exists or not by means of the partial discharging amount of a first cable sample, if not, calculating the isothermal relaxation current according to a second cable sample, acquiring aging factors, calculating the activation energy of XLPE according to a third cable sample, adopting the aging factors and the activation energy of XLPE as common criterion, and acquiring whether aging of the cable to be tested exists or not and the severity of the aging state. The cable insulation aging state can be determined by the isothermal relaxation current method and the activation energy method comprehensively, the defect that large determination errors are produced since the XLPE insulation cable aging state is determined by one single indicator is overcome, the more accurate estimation of the XLPE cable insulation aging state is provided by combining the electric quantity (aging factors) and non electric quantity (activation energy), and the method is simpler.