The invention provides a method for preparing high-purity isobutane, n-butane and butene from mixed carbon 4. The method comprises the following steps of: feeding the mixed carbon 4 into the middle of an isobutane tower, feeding a first path of cyclic solvent into the upper part of the isobutane tower, obtaining isobutane on the top of the isobutane tower, and directly feeding extract on a tower kettle into the middle of an n-butane tower; feeding a second path of cyclic solvent into the top of the n-butane tower, obtaining n-butane the top of the n-butane tower, and feeding extract on the tower kettle into a stripping tower; obtaining butene on the top of the stripping tower, and obtaining the cyclic solvent on the tower kettle; and feeding the cyclic solvent into the isobutane tower and the n-butane tower in two paths. By the process, energy consumption can be greatly reduced.