The utility model discloses a support device relates to engineering machine tool field for the self -adaptation aperture changes. This support device includes skeleton body, support component and elastic component, the skeleton body is equipped with the hole, and the support component passes the hole, and the first end position of support component is inboard in the skeleton body, and the second end position of support component just is used for replacing the inner wall of treating the inspection hole outside the skeleton body, the one end of elastic component links to each other with the skeleton body is fixed, and the other end is connected with the support component, wherein, the elastic component is used for applying support component along the outwardly directed power of through -hole that makes to the support component. Above -mentioned technical scheme can realize that support device treats the self -adaptation of inspection hole internal diameter size, and the cooperation detects the accurate measuring that straightness accuracy, circularity, the depth of parallelism, axiality isoparametric can be accomplished to the device.