In order to improve the material dispersion and reduce the probability of collision and aggregation of particles in a turbo air classifier, compared to a single layer spreading plate, a new double layer spreading plate based on theoretical analysis on the material dispersion is presented in this paper. Discrete phase simulations between the single and double layer spreading plates are implemented using Fluent 6.3.26. The different travelling time of particles via the upper and lower plates indicates the double layer spreading plate can improve the material dispersion and the simulated Tromp curves of the single and double spreading plates also show the cut size and the imperfection are decreased while the sharpness of separation is increased for the turbo air classifier with the double layer spreading plate. Calcium carbonate classification experimental results are in agreement with the simulated results. Compared to single layer spreading plate, the cut size can be decreased up to 25.24% and the sharpness of separation can be increased up to 52.47% for double layer spreading plate, and the imperfection of Tromp curve for double layer spreading plate is smaller that means it closer to the ideal classification curve. It shows the double layer spreading plate put forward in this paper can effectively improve the material dispersion in the classifiers. (C) 2017 Elsevier B.V. All rights reserved.