Impacts of bromide type, concentration, and addition mode on mercury oxidation in coal-fired flue gas from a drop-tube furnace was investigated. The experimental results indicated that bromine promoted mercury oxidation in coal-fired flue gas. The oxidation rate increased rapidly in a specific bromine concentration range and slowed when the concentration exceeded the range. This optimal range varied by coal quality and bromide type. Regarding the cost, operability and effectiveness of the bromine addition mode, the effectiveness followed the sequence post-combustion HBr injection < pre-combustion HBr injection < CaBr2 addition to coal < NaBr addition to coal. The highest mercury oxidation rate for lignite (72%) was obtained by adding NaBr at 200mg/kg, and the highest rate for sub- bituminous coal (83%) was obtained by adding NaBr at 1000mg/kg.