Abstract: In order to improve the sizing performance of starch sizes and decrease the dosage of PVA,nanosized inorganic size additives can be used in the formulation of starch solution.In the present work,the mechanism of nanosized inorganic size additive used in warp sizing was investigated by using SEM,AFM and FT-IR ATR.The results showed that the nanoparticulates can improve the smoothness and uniformity of starch size film and broken cross-section as well as the surface of sized warp yarns.Substantive hydrogen bonds between the nanoparticulates and starch molecules exist,which may be attributed to the enriched hydroxide groups on the surface of nanosized oxides.