Four types of iron in-situ-impregnated mesoporous activated carbons (FGL1/2/3/4) have been prepared by iron-impregnation and two-step steam activation using coal-blending as precursors. And surface modified carbons (Fe-GL-2/3/4) were prepared by iron impregnation based on finished blank carbon C-GL (without iron impregnation). Adsorption of arsenic ions (As (Ⅲ) and As (V)) and humic acids (HA) from water by iron in-situ-impregnated carbons were investigated in comparison with surface modified carbons. Results suggested that iron in-situ-impregnation was beneficial for development of surface area (S_BET) and mesoporous structures. When iron content reached to 6.51%, mesoporous volumes (V_mes) from 45 to 480Å of FCL4 increased by 0.1146cm³/g in comparison with C-GL. However, surface modified by iron impregnation resulted in the decrease of S_BET and V_mes. Surface basicity ensured higher arsenic adsorption capacities by iron in-situ-impregnated carbons in neutral environment. Langmuir maximum adsorption capacities (L-Q_max) of As (Ⅲ) and As (V) by FCL4increased to 2.566 and 2.825mg/g, respectively. It indicated that adsorption capacity of HA (<10mg DOC/L) was significantly influenced by V_mes, and iron in-situ-impregnated carbons achieved better capacities for HA. Langmuir maximum adsorption capacities of HA (Q_HA) obtained by FGL4increased to 46.25mg DOC/g, but capacities by Fe-GL-4decreased to 22.15mg DOC/g. Adsorption capacities of arsenic and HA decreased in Arsenic-HA system. However, FGL4 still obtained higher capacities than C-GL and Fe-GL-2/3/4. And L-Q_max of As (Ⅲ)/As (V) by FGL4 was 2.325/2.675mg/g. Therefore, iron in-situ-impregnated mesoporous carbons prepared in present work are proved to be promising adsorbent for simultaneous removal of arsenic and humic acids.