The relationship between the granular wafer movement on a two-dimensional conveyor belt and the size of the exit together with the velocity of the conveyor belt has been studied in the experiment. The result shows that there is a critical speed v(c) for the granular flow when the exit width d is fixed (where d=R/D, D being the diameter of a granular wafers). When v<v(c), the outflow rate Q increases linearly with the speed v and the flow rate Q=rho(v)R. The turning point of the Q-v curve occurs at the speed v(c). The critical speed v(c) is dependent on the exit width d. When v>v(c), the flow rate Q is described as Q=Crho(v)(beta)(d-k)(3/2). These are the effects of the interaction among the granular wafers and the change of the states of the granular flow due to the changing of the speed or the exit width d.