The invention discloses an outburst prediction method and device based on the size distribution condition of drilling coal dust. According to the method, high-pressure airflow is utilized to impact coal dust, under the action of the airflow, the smaller the particles are, the farther the drifting distance is, otherwise, the larger the particles are, the closer the drift distance is. The proportions of the coal dust with different drift distances are the real reflection of the size distribution condition of the coal dust. Finally, the proportions of the coal dust at different drift distances asa curve, a feature value of a relation curve of the drift distances and the proportions of the coal dust is found out by combining a Rayleigh distribution probability density function and the curve.Therefore, the size distribution condition of the coal dust is reflected through the feature value, and the feature value is taken as a prominent prediction index.