The invention discloses a system and method for increasing recovery ratio of water drainage and gas production by gas lift in a deepwater gas field. The system comprises a gas well gas lift portion, a jet device pressurizing portion, an ethylene glycol injection system and an underwater control unit; the gas well gas lift portion comprises a downhole gas lift valve, a gas lift flow regulating valve and gas lift auxiliary pipelines; the jet device pressurizing portion comprises a deepwater high-pressure jet device, an ejected gas flow regulating valve and auxiliary pipelines; the ethylene glycol injection system comprises an ethylene glycol injection valve and liquid fly lines; the underwater control unit collects signals of the gas well gas lift portion, the jet device pressurizing portion and the ethylene glycol injection system and controls the gas well gas lift portion, the jet device pressurizing portion and the ethylene glycol injection system; the underwater control unit is in communication connection with an offshore production platform control system through an umbilical cable, so that a conventional scheme of an underwater centrifugal electric compressor is replaced, the later development cost of the deepwater gas field is reduced, the abandonment pressure of an underwater wellhead is reduced, the productive life is prolonged, and the recovery ratio of a gas well is increased.