The invention discloses a positioning method for single-phase earth fault sections of an isolated neutral system. The method comprises the following steps: firstly, collecting synchronous stable zero sequence current instantaneous values at two ends of the previous section of a to-be-detected line; calculating the difference value of the two synchronous stable zero sequence current instantaneous values; and determining the fault position regions by virtue of the polarity of the difference value and polarities of the two zero sequence current instantaneous values. The method disclosed by the invention can be used for positioning the fault regions for the condition that a transitional resistance is relatively great and the change of length of the line is inconsistent in the system and has a low requirement on the precision of equipment, so that the accuracy of positioning the fault regions is improved.