A road traffic jam early warning method includes: performing characteristic classification according to acquired multi-source traffic data, and constructing a corresponding characteristic membership function, to obtain a first fuzzy weight; applying an expert evaluation method to the multi-source data to construct an artificial membership function, and calculating a second fuzzy weight; performing fuzzy weighted average on the characteristic membership function according to a fused fuzzy weight obtained by fusing the first fuzzy weight and the second fuzzy weight, and performing defuzzification on obtained weighted average membership functions having different characteristic quantities, to obtain fused multi-source traffic data; constructing a road traffic congestion model, and calculating an optimal road traffic congestion index; and acquiring current multi-source traffic data, predicting a current congestion index, and providing, by comparing the current congestion index with the optimal road traffic congestion index, a warning about whether a current road is congested.