Two kinds of Fe-Mn oxide impregnated GAC (FM-GAC-1, FM-GAC-2) were prepared and their arsenite removal performance were studied. The adsorption isotherm and reaction kinetic models of arsenite on the two kinds of modified GAC and influence of solution pH, temperature and co-exist anions were investigated in the study. The results showed FM-GAC-1 and FM-GAC-2 can adsorb arsenite effectively, the adsorption capacities were 32.37 mg x g(-1) and 26.67 mg x g(-1) respectively. The adsorb velocity could be predicted well by applying pseudosecond order rate equation and the chemistry reaction process was the limitation of the reaction for both modified GAC. The lower solution pH was benefit to the removal of arsenite. The adsorption capacity of FM-GAC-1 and FM-GAC-2 decreased with temperature increasing. The adsorption processes were spontaneous heat-discharge processes. Some co-exist anions can influence arsenite adsorption on modified GAC when their concentration were 200 times of arsenite. It was found that SiO3(2-), PO3(2-), NO3(-) had a significant negative influence on arsenite removal by FM-GAC-1 and SiO3(2-), CO3(2-) can markedly decrease arsenite adsorption on FM-GAC-2. As a whole, FM-GAC-1 had better arsenite removal performance than FM-GAC-2.