The invention relates to a single-phase earth fault line selection distance measurement method for a power distribution line based on the calculation of transition resistance characteristics. The method comprises the steps: injecting one periodic signal different from a power frequency signal into a power distribution system, and carrying out sampling; calculating transition resistance; and carrying out the analysis and calculation of a single-phase earth fault of a power distribution network through employing the characteristic that a transition resistor is purely resistive. The method opens up a new solution to the research of a single-phase earth fault line selection and distance measurement method, and has great theoretical and actual application values. According to the invention, a line model employs a distribution parameter model, and the distribution parameter model of the line gives consideration to the effect of a distributed capacitor, does not need to achieve centralized equivalence, and can precisely represents the characteristics of the line. Therefore, the distribution parameter model of the line can remarkably improve the precision of analysis and calculation results.