A novel nano-TiO_2-_xN_x composite was used as photocataiyst and added to the interior wail paint.The average diameter of nano-TiO_2-_xN_x was about 20 nm.The majority crystal component of the sample was anatase and its optical absorption edge was shifted from 387 nm to 520 nm significantly.Nano-composite paint containing different dosage of nano- TiO_2-_xN_x was investigated to study the properties of formaldehyde decomposition in the air.Testing results show that the formaldehyde decomposition ratio of that nano-paint can almost reach above 80%,especially for that of the paint contain- ing 3% (w/w) nano-TiO_2_xN_x,which exceeded 90%.The primary investigation on the reaction kinetics of photocatalytic formaldehyde decomposition indicated that the experiment data well fit the model of first-order reaction kinetics.