The invention provides a method of determining the maximum allowable resistance leakage current of a zinc oxide arrester. The method comprises steps: a three-dimensional solid model for the zinc oxide arrester is built; a mesh is divided; mesh attributes and boundary conditions of the zinc oxide arrester three-dimensional solid model are set, and the actual working voltage of the zinc oxide arrester is loaded; the potential of the zinc oxide arrester in the actual operation condition under the actual working voltage is calculated, the potential value of each zinc oxide resistor of the zinc oxide arrester is acquired, and the capacitance leakage current value of the zinc oxide resistor is acquired; the resistance leakage current flowing through the zinc oxide resistor under different resistivity is calculated; the relationship between the resistance leakage current change condition and the zinc oxide resistor resistivity is obtained; and the maximum allowable resistance leakage current is calculated. Through calculating the resistance leakage current change rate of the zinc oxide arrester, the wetting degree of the zinc oxide arrester is judged, the fault condition of the zinc oxide arrester can be evaluated, and effective early warning on the zinc oxide arrester can be realized.