Abstract: It is noted that the run-out and deposition processes of rockslide-avalanche can be greatly affected by the width of the depositing zone. However, there are limited studies regarding the influence of the width of the depositing zone on the run-out and deposition processes of rockslide-avalanche in literature. In this study, a model test system with an easily adjustable width of the depositing zone is designed and used for a series of model tests. During the tests, the images and data of the run-out process and deposition behaviors, with different widths of depositing zone, are collected and used for deriving the velocity and deposition behaviors of the granular flow. Further, numerical simulations are undertaken to reveal the underlying mechanisms of the run-out and deposition behaviors. On the basis of the obtained results, the following conclusions are drawn. The divergence of the sliding materials on its inclined sliding path tends to increase with the sliding distance. The sliding velocity of the materials in the depositing zone decreases with the width of the depositing zone, the sliding direction of the materials changes in the depositing zone and this change becomes more distinct with the increase of the width of the depositing zone. The increase of the width of the depositing zone tends to lead to the decrease of the length of the granular flow deposition in the depositing zone while the increase of the width of the granular flow deposition. The area of the granular flow deposition decreases first and then increases with the width of the depositing zone. Numerical simulations indicate that collision is the main type of energy transfers among the sliding martials while friction is the main type of energy consumption. With the increase of the width of the depositing zone, the frequency of collisions decreases and the sliding materials tends to move towards two sides. The energy consumption induced by friction could lead to the increase of the width of the granular flow deposition while the decrease of the deposition length.