The invention relates to a heat-insulating device for an optical fiber preform. The heat-insulating device comprises a base frame, a heat-insulating box hood, a supporting frame and a lifting mechanism, wherein the bottom of the heat-insulating box hood is open; the heat-insulating box hood can hood the base frame; the supporting frame is used for supporting and suspending the optical fiber preform in the heat-insulating box hood; the supporting frame is fixed to a base; and the lifting mechanism is used for lifting the heat-insulating box hood. According to the heat-insulating device for theoptical fiber preform, through the liftable heat-insulating box hood, a heat field is provided from the upper side and the side surface of the optical fiber preform so as to avoid the problem that a furnace core tube is damaged due to rupture and dropping of the optical fiber preform during heat insulation, so that the maintenance cost is reduced; and in addition, after completion of the heat insulation, the heat-insulating box hood is lifted and the optical fiber preform can be directly grabbed and transferred by a mechanical arm, so that the time is saved and the production efficiency is improved.