Abstract: It is presented that the mixing level of flowing liquid in top vessel with batch distillation under total reflux and top accumulation i s represented by means of the stags of multistage mixing flow in series model, and its basic equations and numeric algorithm of batch distillation of binary ideal mixture under ideal operation condition are given. The effects of the m ixing level of flowing liquid in top vessel with batch distillation under the o peration method on the energy consumption is discussed by the calculated results of examples.