The invention discloses a method for preparing high-purity butanedinitrile by reactive distillation. A reactive rectification device is adopted, the structure of the device comprises a reaction distillation kettle, a top output tube at the top of the reactive distillation kettle is connected with a condenser, the condenser is connected with a storage tank, the return tube of the storage tank is connected to the middle portion of the reactive distillation kettle, and a bottom connecting tube at the bottom of the reactive distillation kettle is connected with a reboiler. Acrylonitrile, hydrocyanic acid and triethylamine are used as reaction raw materials, the temperature is controlled at 50-70 DEG C, the acrylonitrile and triethylamine are fed from the upper end portion of the reactive distillation kettle, and the hydrocyanic acid is fed from the lower end portion of the reactive distillation kettle; and the bottom of the reactive distillation kettle is sampled, the obtained sample is detected, and when the mass fraction of butanedinitrile subjected to solvent removal exceeds 97%, the reaction is stopped, a material at the bottom of the reactive distillation kettle is discharged intothe reboiler, and the solvent is distilled off to obtain the target product butanedinitrile. The method has the advantages of integration of the reaction and the distillation, high reaction efficiency and good selectivity.