The invention provides an electrical load prediction method and system based on big data. The method comprises the steps of acquiring weather forecast data of an electrical region based on predictiontime; and substituting the prediction time, the electrical region and the weather forecast data into a pre-established prediction training model to obtain a historical prediction electrical load within the period of prediction time, wherein the prediction training model is determined by a training characteristic dataset of the electrical load, the time and the weather data based on a GBDT (Gradient Boosting Decision Tree). According to the electrical load prediction method and system based on the big data, an operation of writing intermediate data into a memory is implemented through the big data, the computational efficiency is greatly improved for the system for implementing the effect that the data are processed in real time, and the problems that the historical mass electrical load data cannot be rapidly acquired, processed, analyzed and stored in a conventional method can be well remedied through a big data analysis technology.