The invention relates to the technical field of preparation of high-purity silicon monoxide, in particular, relates to a method and device for preparing high-purity silicon monoxide by a medium-frequency induction heating way, and is characterized in that the preparation method comprises the following steps: 1, preparing raw materials: mixing high-purity silicon with the content of more than 99.5 wt% and silicon dioxide with the content of more than 99.5 wt% according to the weight ratio of 1:1; 2, carrying out medium-frequency induction heating; and 3, cooling to obtain the finished product; when the medium-frequency induction heating temperature is 1200-1600 DEG C, the molar ratio of the raw materials of high-purity silicon and silicon dioxide is adjusted, and the value of x in the product SiOx is a fixed value; but when the medium-frequency induction heating temperature is more than or equal to 1600 DEG C, the value of the molar ratio of the raw materials of high-purity silicon and silicon dioxide is controlled to be 0.88-1.2, and the value of x in the product SiOx is adjustable in a range of 0.89-1.10. Compared with the prior art, the method and the device have the advantages of high heating efficiency and stable equipment; products with different silicon-oxygen ratios are obtained by adjustment of the heating temperature and the ratio of the raw materials.