A method for recovering CO2 in the Rectisol process. The method includes at least the following steps: performing reduced-pressure flash distillation treatment on the CO2-rich methanol liquid, and outputing the CO2 desorbed gas obtained after the reduced-pressure flash distillation treatment as a product gas; performing heat exchange flash distillation treatment on a first methanol treatment liquid obtained after the reduced-pressure flash distillation treatment, and outputing the CO2 desorbed gas obtained after the heat exchange flash distillation treatment as a product gas; performing vacuum flash distillation treatment on a second methanol treatment liquid obtained after the heat exchange flash distillation treatment, and outputing the CO2 desorbed gas obtained after the vacuum flash distillation treatment as a product gas. Reduced-pressure flash distillation treatment, heat exchange flash distillation treatment and vacuum flash distillation treatment are sequentially performed on the CO2-rich methanol liquid in this method.