Abstract: Electricity theft not only results in national revenue losses and potential safety hazards within the distribution network but also complicates the tasks for power personnel.In order to explore efficient and variable anti-electricity theft technologies, this research employs the forward and backward substitution method to calculate the power flow within the distribution network circuit.This method enables the determination of line loss values and identification of suspected electricity theft locations.Furthermore, it calculates the voltage offset rate and correlation degree to accurately pinpoint instances of electricity theft, assessing the variance between supplemental and actual power to qualify stolen electricity.Through experiments and case studies, a notable enhancement of approximately 30% in the efficiency of power flow calculation using this method has been demonstrated.Analysis of electricity consumption examples among high and low voltage users revealed three instances of electricity theft, with an average voltage correlation value of approximately 0.35,indicating deviation from the normal correlation value.These findings validate the efficacy of the forward and backward substitution method in anti-theft technology, providing a valuable insights for the implementation of anti-theft measures within the power system.