The zero sequence impedance of the cable changes with the zero sequence current as the zero sequence current flows in the ground and the sheathing simultaneously. If the constant zero sequence impedance is used to set the current， the zero sequence current protection can not operate correctly. Considering the zero sequence impedance of the cable to be the function of the current， the adaptive zero sequence current protection is proposed based on iterative algorithm. The initial value is obtained according to the empirical formula. The zero sequence impedance is solved through the fitting of the impedance-current curve by the least square method. The setting value of the protection is finished automatically by the protection device and adapts well the present operation mode of the power system.