A novel operation of batch distillation-combination of varying column pressure and total reflux-total efflux is studied experimentally. In the operation, the product is accumulated at the tot) of the column under total reflux and then drained off completely, and the column pressure is varying in the whole process. This process has been industrialized successfully with large profits. The conventional mode of batch distillation is improved by this method effectively: the separation efficiency and the yield of product are increased greatly, the operation time is shortened and the production cost is cut down. Moreover, the amount of condensation water is decreased and the over-high reboiler temperature is lowered.