Abstract: An extended mathematical model of the material flow trajectory in free-space was developed to investigate the burden distribution process of COREX shaft. The influence of burden layer distribution of depth and width on the chute and the elaborating charging profile by multiple-linearization were considered in the model. The results showed that the flow trajectory of particles in free-space is determined mainly by the burden layer depth and particle size at the bottom of the chute. The terminal velocity of leaving chute is proportional to the rotation velocity and inverse dependence on the angle of the chute. The distance from the landing position of burden particle to the shaft centre at near throat increases with the increasing of the angle and rotation velocity of the chute. The packing process and charging profile under the different conditions of charging pattern and burden materials can be simulated by the model.