The utility model provides a promote mercury and fine particles device of desorption in coordination among wet flue gas desulfurization, it includes wet flue gas desulfurization tower, steam phase transition room, steam system, defroster, sparge water system and washes the waste liquid export, the flue gas inlet of the exhanst gas outlet of wet flue gas desulfurization tower and steam phase transition room is connected, and steam phase transition room independently sets up the outside of wet flue gas desulfurization tower or is located the inside of wet flue gas desulfurization tower, it is indoor that steam system, defroster and sparge water system are located the steam phase transition, and steam system is to the indoor injection ordinary pressure saturated steam of steam phase transition, and the exhanst gas outlet department in steam phase transition room is established to the defroster, and the sparge water system is used for washing the defroster, wash the bottom that the waste liquid export is located steam phase transition room. The utility model discloses can make the wet flue gas desulfurization device have the efficiency in coordination with desorption fine particles and mercury, but wide application in coal fired power plant wet flue gas desulfurization have huge economic benefits and social.