The invention provides a device and a method for moisture recovery and gypsum rain control in wet desulphurization flue gas of a thermal power plant. According to a process, air is sucked into a flue and/or chimney by utilizing the specially designed flue and/or chimney through an own pullout force of the flue and/or chimney, and mixed with flue gas to reduce the temperature of the flue gas and enable water vapor in the flue gas to be condensed into liquid water which is recovered or reduce the condensation of the water vapor in the flue gas in the chimney. By using the device and the method, under the condition of not needing to arrange a separate device, the reduction of the water vapor in the recovered flue gas and a function of removing the liquid water carried in the flue gas at an outlet of the chimney are realized, meanwhile, the formation of the gypsum rain is inhibited, and the operation cost and equipment complexity are reduced.