The invention provides an overhead line dynamic current-carrying capacity advanced prediction method and system, and the method comprises the steps: obtaining the meteorological historical data of thesurrounding environment of an overhead line, and converting the meteorological historical data into time sequence data with the same time interval; training and learning the time series data by adopting a recurrent neural network introducing an attention mechanism to predict the meteorological data of the surrounding environment of the overhead line in the future; according to the prediction result of the meteorological data, in combination with a steady-state heat balance equation, giving overhead line model parameters and the highest allowable temperature thereof, and calculating the dynamic current-carrying capacity and the transmission capacity of the overhead line; respectively predicting a plurality of monitoring points of the overhead line and calculating the dynamic current-carrying capacity and the transmission capacity, and taking the minimum value of all the monitoring points as the final result of the dynamic current-carrying capacity and the transmission capacity of the overhead line at the moment. A recurrent neural network of an attention mechanism is introduced for prediction, so that a training model selectively pays attention to input strongly related to a target, and the prediction precision is improved.