Abstract: The pulverized coal was adhered to the wall of convergent and throat section and formed a hard layer when concentrated gas coal flew through Venturi, which resulted in a decrease in the conveying capacity and an increase in the total pressure drop of Venturi. The results from the industrial normal analysis, XRF, XRD, SEM and EDS showed that the accumulation contained relatively more content of mineral mainly consisted of Kaolin and major mineral elements compared to the pulverized coal. The inner layer of the accumulation was relatively flat, while in the outer layer there contained the least amount of mineral element and the most amount of carbon element. Compared to the straight part of the pipe, the coal particles were forced to flow more closely to the wall inside convergence and throat inlet section which is easier to form hard layer.