The modification of the traditional interior wall paint was carried out by means of adding nano-TiO2 as a functional pigment. By regulating the dosage of dispersant, the nano-particles can be dispersed in paint homogeneously. With two aspects of experiments： dosage of nano-TiO2 and pigment volume concentration （PVC）, the paint formulation can be optimized and its properties~ such as hardness, scrub resistance, storage stability, contrast ratio and gloss can be improved. Finally an interior wall paint with high performance and air purification was prepared. Its character of formaldehyde degradation would be discussed in the next article.