The difficulty in the removal of mercury in flue gas of combustion processes is mainly due to the high volatility of elemental mercury. Various sulfide compounds were tested to check which compounds can convert mercury into stable mercury sulfide and remove mercury from flue gas. The results indicate that lead, cadmium, copper, antimony, tungsten, molybdenum, and palladium sulfides removed more than 80% of mercury from synthetic gas with mercury. On the other hand, zinc, silver, barium, calcium, and nickel sulfides were not effective for mercury removal and their removal efficiencies were less than 20%. The surface analysis using X-ray photoelectron spectroscopy suggested that mercury which reacted with sulfide compounds was presumed to form black mercury sulfide.