The invention discloses an electric quantity supplementing method based on clustering and a PQUI recognition algorithm, and relates to the field of power grid operation and maintenance. At present, the electricity stealing amount cannot be accurately calculated, the difference between the calculated electricity stealing amount and the actual electricity stealing amount is too large, and users andelectric power companies are difficult to keep fair. According to the invention, the electricity stealing time of the user is judged according to the load data of the user, then the electricity stealing manipulation is determined according to the relationship between the load data, the correction coefficient is determined according to the electricity stealing behavior, and finally the compensationelectric quantity is calculated according to the correction coefficient. And a clustering algorithm and/or a PQUI algorithm are/is adopted during calculation of the number of electricity stealing days. According to the technical scheme, the clustering algorithm and the PQUI recognition algorithm are adopted to calculate the corresponding electricity stealing amount, the calculation matching performance is good, the accuracy is high, the collected data can meet the requirements, the supplementary electricity amount of the electricity stealing user can be accurately, objectively and quickly calculated, the supplementary electricity amount is made to be consistent with the actual electricity amount, and the fairness of electricity utilization is improved.