The invention discloses a control and optimization method of an external/internal thermally coupled distillation tower. As for the external thermally coupled distillation tower, a high-pressure distillation tower and a low-pressure distillation tower keep constant pressure operation; the quality of a product positioned on the top of the low-pressure distillation tower is controlled by the reflux quantity of the low-pressure distillation tower; the quality of a product positioned at the bottom of the low-pressure distillation tower is controlled by flows extracted from the low-pressure distillation tower to a bottom heat exchanger; the quality of a product positioned at the bottom of the high-pressure distillation tower is controlled by thermal loads of a reboiler of the high-pressure distillation tower; and the quality of the product positioned on the top of the high-pressure distillation tower is controlled by the flows extracted from the low-pressure distillation tower to a top heatexchanger. As for the internal thermally coupled distillation tower, the quality of a product positioned on the top of the internal thermally coupled distillation tower is controlled by the flows extracted from a stripping section to a top heat exchanger; and the quality of a product positioned at the bottom of the internal thermally coupled distillation tower is controlled by the flows extractedfrom the stripping section to a bottom heat exchanger. According to the control and optimization method disclosed by the invention, the stable operation of the external/internal thermally coupled distillation tower can be maintained under the precondition of ensuring the qualities of the products, and an optimal steady-state operation condition is achieved.