Disclosed herein is an ink cartridge refill system for inkjet printers and a method of refilling ink cartridges using the system. The refill system includes a vacuum pump to supply ink from an ink tank into a cylinder and to forcibly draw ink from an ink cartridge, as well as an air compression pump to generate a compression force to inject ink from the cylinder into the ink cartridge through the nozzle of the cartridge. The cylinder is connected at the inlet end thereof to both the air compression pump and the vacuum pump, and is connected at the outlet end to both the ink tank and the ink cartridge. Both a compression pump line and a first vacuum pump line which pass through the cylinder are connected to the nozzle of the cartridge through an ink supply hose. The vacuum pump includes a second vacuum pump line directly connected to the ink cartridge, as is the first vacuum pump line passing through the cylinder. Both the ink supply hose and the second vacuum pump line are connected to the nozzle of the cartridge through a connection unit. The refill system can regulate the inner pressure of a refilled cartridge by removing predetermined small amounts of air and ink from the refilled cartridge, and can completely remove waste ink from the cartridge at the initial stage of a cartridge refill process when necessary.