ABSTRACT A trapezoidal gas-solid fluidized bed separation system was designed to improve the separation space and processing capability of the gas-solid separation fluidized bed by combining inclined air distribution plates with horizontal air distribution plates. The distribution pattern of bed density was investigated under different operational conditions. The results showed that the operational conditions significantly influenced the standard deviation of bed density fluctuation and the skewness of bed density. When the fluidization number of the horizontal section and inclined section are 1.4 and 1.2 respectively, the aperture of the distributor plate is 6–2 mm, and the static bed height is 150 mm, the minimum standard deviation of bed density fluctuation (Sρ) is 0.07 g/cm3, and the skewness of density fluctuation (SKρ) was less than 0, indicating good fluidization quality of the bed under these conditions. Experimental separation tests of 13 ~ 6 mm raw coal were conducted in both the horizontal section of the bed and the overall trapezoidal fluidized bed, and the results showed that under the operational conditions with the best stability of bed density, ash separation was most prominent, with a possible minimum deviation (E) value of 0.120 g/cm3. Furthermore, under the same operational conditions, the maximum processing capacity of the horizontal bed section was 300 g, while the trapezoidal gas-solid fluidized bed with inclined air distribution plates could achieve a maximum processing capacity of 400 g, indicating that the trapezoidal gas-solid fluidized bed effectively expanded the separation space.