Aspen Plus software was used to simulate an ethylene tower system before and after the modification of a 1.1 Mt/a ethylene plant. Aiming at the high ethylene loss at the bottom of ethylene tower during production, the heat load of heat exchanger was analyzed from a process point of view, and the hydraulic model of ethylene tower was analyzed from an equipment point of view. Combined with the actual operation on site, some optimization measures were proposed. The flooding in distillation section can be solved by reducing the middle boiling and increasing the bottom boiling. By lowering the liquid sampling point in condensate tank D-410, appropriately raising the outlet pressure of the 4^th stage of ethylene refrigeration compressor or appropriately reducing the temperature of hot stream to strengthen the phase change heat transfer, the flow rate of hot stream can be increased, thus meeting the required heat load.