The composite element method（CEM） is utilized to mix wood fiber and activated carbon into the self-adsorption fiber board under certain process condition. The density, bending strength, elastic modulus, internal bond strength and water absorption are tested under the same condition, at the same time, the formaldehyde emission rate is measured with desiccator method. The result shows that all the mechanical properties of self-adsorption fiber board are a bit higher than that of ordinary fiber board. The effect of formaldehyde self-absorption is highly related to the amount of added activated carbon instead of the form. Under the test condition, the emission of formaldehyde of the self-adsorption fiber board added with 10% activated carbon grain can be reduced by 35%. Further more, it is easier for the self-adsorption fiber board added with powder activated carbon to obtain even physical and mechanical performance and absorption effect.