An industrial vertical tank (cost $200,000) was produced to recover the heat of sinter ores in our laboratory, the voidage along the height direction needs to be studied in order to determine the best height of sintering layer in it. In this paper, the bulk bed voidage of sinter ores in cylindrical polyvinylchloride tube (PVC-U) was measured by the cross-section image analysis method. The large-diameter tube was used to minimize the wall effects so that we could measure the bulk bed voidage in the center of the tube. The results show that the new method is useful, the voidage increases at lower height and fluctuates slightly between 0.36 and 0.43 in a stable stage, the voidage increases as particle size increases, decreases as the shape factor increases, and increases as the tube to particle diameter ratios decreases. These provide significant voidage data for the study of a vertical tank.