There is provided a method for continual preparation of granular polycrystalline silicon using a fluidized bed reactor, enabling a stable, long-term operation of the reactor by effective removal of silicon deposit accumulated on the inner wall of the reactor tube. The method comprises (i) a silicon particle preparation step, wherein silicon deposition occurs on the surface of the silicon particles, while silicon deposit is accumulated on the inner wall of the reactor tube encompassing the reaction zone; (ii) a silicon particle partial discharging step, wherein a part of the silicon particles remaining inside the reactor tube is discharged out of the fluidized bed reactor so that the height of the bed of the silicon particles does not exceed the height of the reaction gas outlet; and (iii) a silicon deposit removal step, wherein the silicon deposit is removed by supplying an etching gas into the reaction zone.