Mercury speciation and emission from two Chinese coal-fired power stations equipped with flue gas desulfurization device were investigated. Research results reveal that Hg-0 is the main form in the flue gas in Plant 1; Hg2+ is the main form in the flue gas in Plant 2. Most of mercury was emitted to the atmosphere, which was about 77-98%, and the elemental mercury released to atmosphere ranged 73-94% approximately. A pot of mercury is adsorbed by bottom ash, electrostatic precipitator (ESP) ash, and gypsum in Plant 1. However, most mercury, the scale of which is 75-83.2%, is collected by ESP ash, and only 7.0-12.2% mercury is emitted to the atmosphere in Plant 2. The mercury removal by NID semi-desulfurization system is higher than wet flue gas desulfurization (WFGD) desulfurization system.