The invention provides a variable-frequency vibration isolator. The variable-frequency vibration isolator is mainly composed of an upper mounting panel structure, a middle metal plate, a lower mounting panel structure, an inner rubber ring cylinder, an upper rubber ring column and a lower rubber ring column. The upper rubber ring column sleeves the upper portion of the inner rubber cylinder, and the inner side of the upper rubber ring column and the outer side of the inner rubber cylinder are bonded. The upper mounting panel structure is in vulcanized joint with the top of the inner rubber cylinder and the top of the upper rubber ring column. The lower rubber ring column and the middle metal plate sleeve the lower portion of the inner rubber cylinder, and clearances are reserved between the lower rubber ring column and the inner rubber cylinder and between the middle metal plate and the inner rubber cylinder. The top of the outer rubber ring column and the lower surface of the middle metal plate are in vulcanized joint. The lower mounting panel structure is in vulcanized joint with the bottom of the inner rubber cylinder and the bottom of the lower rubber ring column. The variable-frequency vibration isolator is provided with the inner rubber cylinder, the middle rubber ring column and the outer rubber ring column with the rigidity increased step by step, and the aim of frequency conversion of the vibration isolator is achieved.