Abstract: Algorithm of the minimum total vapor capacity of batch distillation of ideal binary mixture under total reflux and top accumulation and ideal operation condition is developed.A function f(x _D) [equation(7)]is set up and transformed into g(x _D)[equation(10)]in order to determine that the instantaneous constant region is on the top(or in bottom).For designed separation task,the method for determining the interval of x _D in which the instantaneous constant region is on the top(or in bottom)and the equations for calculating minimum total vapor capacity are derived.