The present disclosure discloses a method for preparing an isolation area of a gallium oxide device, the method comprising: depositing a mask layer on a gallium oxide material; removing a preset portion region of the mask layer; preparing an isolation area in a position, corresponding to the preset portion region, on the gallium oxide material by using a high-temperature oxidation technique, with the isolation area being located between active areas of the gallium oxide device; and removing the remaining mask layer on the gallium oxide material. In the disclosure, the isolation area is prepared by using the high-temperature oxidation technique, which prevents damage to the gallium oxide device during the preparation of the isolation area, thereby achieving isolation between the active areas of the gallium oxide device.