The utility model discloses a drying sterilization device capable of guaranteeing mildew-inhibition and sterilization efficiency. The drying sterilization device comprises a heating device, a vacuum pump and a gas cylinder filled with inert gas, wherein a closed container is arranged in the heating device, and a radius-variable telescopic support is arranged in the closed container; the gas outlet of a gas pipe extends to the bottom of the inner cavity of the closed container. When the device is used, a material to be treated can be put on the telescopic support, and the inert gas disperses upward from the bottom of the inner cavity of the closed container because the gas outlet of the gas pipe extends to the bottom of the inner cavity of the closed container; the inert gas at the bottom of the inner cavity can quickly disperse toward the upper part of the inner cavity because the inner cavity of the close container is of a conical shape with big upper part and small lower part, so that the time of filling the inert gas in the closed container can be shortened, the mildew-inhibition and sterilization effects can be achieved, and the efficiency of mildew-inhibition and sterilization can be further improved. The drying sterilization device is suitable for popularization and application in the field of chemical engineering equipment.