Abstract: To eliminate the systematic deviation between the standard theoretical conveying capacity and the actual conveying capacity in the engineering application of 26° steep-incline trough belt conveyors, a discrete element simulation model is established based on the EDEM software in this study. With belt speed, trough angle, feed mass flow rate, particle density and particle-belt friction coefficient selected as influencing variables, simulation tests are carried out under 30 designed working conditions. The actual conveying capacity is determined by monitoring the mass flow rate at the discharge end within the steady-state period. The deviation coefficient is quantified, and the underlying deviation mechanism is clarified. Meanwhile, a random forest regression model is developed to analyze the influence and coupling effect of various parameters.The simulated results indicate that the actual conveying capacity is obviously lower than the theoretical value under an inclination angle of 26°, and the deviation coefficient varies from 0.12 to 0.60. Belt speed, trough angle and feed mass flow rate are identified as the major positive influencing factors. The findings of this study can provide theoretical references for the design of high-inclination conveying equipment in machine tool workshops, the matching design of chip removal systems, and the optimization of material transportation for workpiece loading and unloading.