The mechanism of the formation of formic acid and sodium bicarbonate by GLLDD has been studied. The absorption rate of CO2 by the organic phase was found to be almost ten times that by sodium formate solution. It was also shown by experiment that the mass transfer of CO2 from the gas phase into the aqueous phase proceeded essentially through the organic phase rather than directly. CO2 was absorbed in the organic phase before reacting with sodium formate solution to form NaHCO3 and complex amine carbonate. The organic phase was both the extractant of formic acid and the transporter of CO2.