Mercury is one of the carcinogenic heavy metals and harmful for human health atvery low concentrations. Modified fly ash, pellet fly ash-chitosan composite absorbs ionic form of Mercury (Hg2+). It is prepared by dissolving 2 g of chitosan in oxalic acid 5%, then20 mL of the solution was added with 4 g of fly ash and cross fastened using 2% glutaraldehyde. The experiments was conducted at pH 2, 3, 4, 5, 6 and stirred in 60, 120, 180rpm for each pH. The result shows optimum absorption Hg2+ found in pH 6 by adsorption capacity 89.9%. Stirring speed 60 and 180 rpm yielded greater adsorption capacities to 88.51% and 91.89% respectively. Key words: adsorption capacity, chitosan, fly ash, mercury.