There is a problem of the low reliability of power supply due to direct tripping of protection after a single-phase grounding fault in a small resistance grounding system. Thus a voltage gradient location method taking into account the phase offset is proposed. First, using the zero sequence current flow loop of a single-phase grounding fault in small resistance grounding system, the zero sequence voltage amplitude distribution characteristics are analyzed when the zero sequence voltage phase offset is ignored and when the zero sequence voltage phase offset is taken into account. Secondly, for the case when the zero sequence voltage phase offset cannot be ignored, the distribution characteristics of the relative amount of zero sequence voltage at any point of the fault line is analyzed by taking the zero sequence voltage at the exit of the bus as the reference. Finally, on the basis of accurately obtaining the sector location results, a location method based on the gradient of the relative amount of zero sequence voltage is proposed. Simulation results show that, for overhead lines with typical parameters, compared with the traditional location method based on zero sequence voltage amplitude gradient, the ranging accuracy is significantly improved by using the gradient of the relative amount of zero sequence voltage.