A power sourcing equipment includes a residual current detection unit, a voltage detection unit, and a controller. The controller determines an insulation resistance value at the input end of the power sourcing equipment based on a first preset voltage parameter value, a first residual current value, a second preset voltage parameter value, and a second residual current value. The first residual current value is a residual current value of the power sourcing equipment when a voltage parameter of the power sourcing equipment includes the first preset voltage parameter value. The second residual current value is a residual current value of the power sourcing equipment when the voltage parameter of the power sourcing equipment includes the second preset voltage parameter value.