PM2.5, formaldehyde and eight volatile organic compounds (VOCs) were observed in six selected newly decorated apartment units to evaluate the influence of the decoration process on the indoor air quality in Xi’an, China. The comparison of indoor and outdoor formaldehyde and VOCs concentrations showed that the outdoor PM2.5 concentration exceeded that indoors during the monitoring process, whereas the indoor formaldehyde and VOCs concentrations exceeded the outdoor concentrations. The levels of formaldehyde and VOCs in different rooms were investigated and the result showed that the formaldehyde and VOCs concentrations in bedroom were the highest. Further, formaldehyde and VOCs concentrations were measured in other 200 rooms decorated within 2 years in Xi’an. The results showed that wallpapering, wooden flooring, and furniture were the major decorating process of formaldehyde and VOCs emission sources. In addition, a health risk assessment of the monitored formaldehyde and VOCs in rooms 1 year after decorating showed that benzene posed the greatest health risk among the assessed VOCs.