Abstract: Modified activated carbon(ACN)was prepared via dipping method with coconut shell activated carbon as precursor and urea and niacinamide as modification agents. Effects of surface chemical properties and pore structure on the adsorption performance of formaldehyde were investigated. The surface morphology, pore structure and surface functional groups were characterized by using scanning electron microscopy, N₂ adsorption isotherm and X-ray photoelectron spectroscopy, respectovely of carbon. The results revealed that the loaded particles appeared on the surface and pore of the modified activated carbon, the specific surface area and total pore volume of the modified activated carbon decreased and the number of amide and quaternary ammonium functional groups and lactone class (-C=O) oxygen functional groups increased. As the mass fractions of urea solution was 9% and the mass fractions of nicotinamide was 0.5%, the modified activated carbon ACN₃ had the most excellent adsorption capacity with the equilibrium adsorption capacity of 0.042 9 mg/g, which was 60.67% higher than that of the original activated carbon (0.026 7 mg/g), and was 2-3 times of commercial activated carbon.