The invention discloses a drainage control system and method for a regenerative system of a low-pressure drainage cooler. The system is characterized in that drained water of a low-pressure heater atsome stage is in fluid communication with a high-temperature drained water inlet of a low-pressure drained water cooler through a first valve and is cooled by the low-pressure drained water cooler andthen drained into a condenser; one part of the drained water of the low-pressure heater at the next stage of the low-pressure heater at some stage is in fluid communication with a low-temperature drained water inlet of the low-pressure draining cooler through a second valve and enters the low-pressure heater at the next stage after being heated and vaporized by the low-pressure draining cooler and is used for heating condensed water; and the other part of the drained water of the low-pressure heater at the next stage of the low-pressure heater at some stage automatically flows to the condenser or the low-pressure heater at next stage through a third valve; and a controller is in signal communication with the first valve, the second valve, and the third valve correspondingly. The drainagecontrol system realizes the purposes of indirectly heating condensed water, reducing the steam extraction amount and improving the unit economy by linkage control of the drainage valve.