The occurrence of slope disasters mainly depends on the terrain slope, size and amount of soil and rock particles, and the presence of heavy rain. If particles erode and entrain soil and rock in the bottom bed as they flow after the slope collapse, a massive avalanche can occur, threatening human life and causing substantial property damage. We employed an experimental approach to investigate the effects of the particle size of granular beds (including column and erodible beds) and the initial aspect ratio on their erosion and deposition behavior in granular collapse flows. We found that the erosion area increases when the particle size of the column bed increases, whereas the particle size of the erodible bed remains the same. The final erosion area increases slightly when the initial aspect ratio increases, and subsequently decreases as the initial aspect ratio increases in the presence of a bigger particle size of the erodible bed. However, when the particle size of the erodible bed is smaller than that of the column bed, the final erosion area increases significantly as the aspect ratio increases. Furthermore, we explored the flow trends of the column and erodible bed particles over time at different locations. For different particle sizes of the erodible bed, the potential energy loss of the column bed may be transformed into erosion of the erodible bed, or may be lost due to the friction and collisions between particles, and thus cannot cause significant variation in erosion behavior.