A novel theoretical model which takes into account the particle property, equipment parameters, particle terminal velocity and Reynolds number was established to describe the separation of particles under critical conditions. Meanwhile, this established model was used to predict the superficial velocity of particle separation in the different spacing of inclined channels. A system was developed to test and verify the model. The correlation coefficient (R-2) and Sum of Squares for Error (SSE) were adopted to evaluate the experimental results. When the ratio of fluid Reynolds number to particle Reynolds number was less than 43, the novel model was proved to be highly accurate in the prediction of the superficial velocity. The results suggested that the novel model provided much better conclusions than does a tradition empirical model. This study provides a theoretical and experimental foundation for the design of industrial inclined channel structure and operating parameters. (C) 2020 Elsevier B.V. All rights reserved.