The invention provides a system for simulating a steady-state flow of an internal thermally coupled air separation column. The system comprises a field intelligent instrument connected with the internal thermally coupled air separation column, a control station, a database and an upper computer, wherein the upper computer comprises a signal acquisition module used for acquiring current working operation data and a solving calculation module. The process for simulating a steady-state flow of the system comprises the following steps of: 1, setting structural parameters and operational parameters of the column, and designating an initial value of feeding air flux; 2, assuming liquid-phase compositions of all column plates; 3, for each column plate, calculating a balancing temperature and gas-phase composition by a bubble point method respectively; 4, for each column plate, calculating an enthalpy of the gas-liquid phase respectively; 5, calculating gas-liquid phase flux of all column plates by formulas(1) and (2); 6, judging whether a formula(4) is true, if so, continuing the operations; and 7, otherwise, updating the liquid-phase compositions of all column plates. The invention alsoprovides a method for simulating the steady-state flow of the internal thermally coupled air separation column. The invention provides the system and the method for accurately simulating the steady-state flow of the internal thermally coupled air separation column.