The invention discloses a PSO-based electric quantity forecasting method, which belongs to the technical field of electric quantity forecasting. The forecasting method of electricity quantity under the policy of cut-off and limited production based on BP model. Firstly, the input data are analyzed and processed. Then, taking historical electricity consumption as independent variable and historicalelectricity consumption as dependent variable to train samples, using PSO algorithm to optimize the weights and thresholds of BP neural network, calculating the prediction accuracy of different parameters, and obtaining the weights and thresholds of BP model with high prediction accuracy; Finally, the BP neural network model is forecasted, the optimized parameters of particle swarm optimization algorithm and the forecasting samples are input to the forecasting model, and the forecasting value is obtained. BP neural network algorithm is optimize by PSO, Considering the influence of air qualityindex, meteorological factors and the output factors of main production stopping and limiting products on electricity consumption, the eigenvector of electricity consumption is studied and trained, and the forecasting effect is proved to be ideal by experiments. A new way of forecasting electricity consumption under the influence of production stopping and limiting policy is provided.