The invention, which belongs to the technical field of power systems, discloses a method and system for detecting electricity stealing. The method comprises: carrying out a household change relationship check process to identify whether the electric energy meter user relationship under the court is normal; carrying out calculation on the electric energy meter with the normal user relationship by using an associated monitoring weighting algorithm to obtain an electricity stealing suspected value; and identifying whether the electric energy meter has the electricity stealing suspicion based on the electricity stealing suspected value. According to the invention, after enhancement of the household change relationship checking of the user relationship file of the court, the misjudgment rate ofthe user stealing electricity is reduced; and according to the associated monitoring weighting algorithm, the electricity stealing suspected value of the user is calculated. Therefore, the powerful technical support is provided for the anti-stealing work, so that the efficiency of electricity stealing verification is improved.