One effective way of improving indoor air quality (IAQ) is by filter and adsorption technology. As a kind of natural air filter and adsorption material, wool fiber can filter and adsorb harmful gases. In order to study the potential capability of wool fiber in improving IAQ, an experiment on the adsorption of formaldehyde and the creation of anions was performed. The results indicate that wool is a good adsorber of formaldehyde at low concentrations. The degradation ratios of wool fabric and the fiber are 74% and 69.3% respectively. The emission measure of the anions is over 3000 per cm3. The relevant mechanism is analyzed and verified. Some basic concepts for developing a natural filter and adsorption material that can improve IAQ are established.