Abstracts：A simple method was proposed to evaluate particles packing efficiency. Based on symmetrical distribution hypothesis, the particles were separated to several narrow size grades to characterize the total system. Through changing upper interval grade void content, the evaluation index E of packing efficiency was calculated to evaluate the system packing efficiency. The availability of the method was tested via coal water slurry experiments. The results indicate that E is available to evaluate particles packing efficiency that is improved by increase of E and coal water slurry concentration. The best value of E is variable for different coal samples. When the parameter n in Rosin-Rammler model is between0.7 and 0.8, E gets its relatively high value, but some exception occurs possibly in multi-grading particles accumulation. The realizable concentration decreases when the sample is oxidized, even using a high E value. The expansion ratio coal water slurry prepared by the same coal sample is consistent.

Keywords：particle; packing; evaluation; coal water slurry; continuous size