The invention relates to a method for separating an isobutyl alcohol and normal heptanes azeotropic system by using pressure swing distillation and a device applicable to the method. The device mainly comprises an atmospheric tower T1, a pressurized tower T2, a condenser C1, a condenser C2, a reflux drum D1, a reflux drum D2, a reboiler R1 and a reboiler R2, wherein the reboiler R1 and the reboiler R2 are respectively connected at the bottoms of the atmospheric tower T1 and the pressurized tower T2, the condenser C1 and the reflux drum D1 are sequentially connected at the top of the atmospheric tower T1, the condenser C2 and the reflux drum D2 are sequentially connected at the top of the pressurized tower T2. The separation steps are as follows: a fresh material first enters into the atmospheric tower T1, an isobutyl alcohol product is extracted at the bottom of the tower, after being condensed through the condenser C1, and collected through the reflux drum D1, part of overhead vapor is back flowed, part of the extract enters into the pressurized tower T2 for a secondary rectification, a normal heptanes product is extracted at the top of the pressurized tower T2, and the material flow at the bottom of the tower cycles to the atmospheric tower T1. The method provided by the invention solves the difficult separation problem that the azeotropic behaviors of the system respectively show up a lowest feature and a highest feature along with the raising pressure, and has the advantages of low energy consumption and high product recovery rate.