Mercury in oxy-coal combustion flue gas may cause liquid metal embrittlement and material failure to aluminum (Al) heat exchangers, which needs to be removed with high efficiency before CO2 compression. Oxidized Hg (Hg2+) is soluble thus can be co-removed with SO2 in WFGD (Wet Flue Gas Desulfurization). However, the dissolved Hg2+ in slurry may also transform to the insoluble elemental mercury (Hg-0) form and re-emitted, resulting a reduction of total Hg capture efficiency in WFGD. This paper experimentally examined the Hg migration across WFGD under high CO2 concentration atmosphere with simulated typical desulfurization slurry. Influences of solids (CaSO4, CaSO3) and anions (Cl-, NO3-, SO32-) in slurry are considered. According to the results, solids of CaSO3 with higher BET surface area are more favored for Hg retention than CaSO4. Slurry pH under high concentration of CO2 was a little bit lower than air combustion atmosphere. The decreased pH in turn hindered Hg retention on both solids while the gaseous Hg-0 emission increased. For anions, 6 mM NO3- and 5 mM SO32- both led to large amount of Hg transformed from CaSO4 solids and liquid into the gas phase. The existence of 20 mM Cl- can retain more Hg in the liquid, especially when NO3- and SO32- coexisted. However, this effect was quite pH sensitive. As to CaSO3 slurry, most of the Hg remained in slurry regardless the existence of other anions and atmosphere. (C) 2016 Elsevier Ltd. All rights reserved.