Abstract: Acrylic copolymer /montmorillonite nano-size(Ⅰ) and poly(vinyl alcohol)/ montmorillonite nano-size(Ⅱ) each with different contents of montmorillonite were prepared respectively in presence of Na~+-MMT by in-situ intercalative polymerization of acrylic acid(AA),acrylamide(AM) and methyl acrylate(MA) in water solution,and by intercalation of poly(vinyl alcohol)(PVA) from solution, for sizing cotton and polyethylene terephthalate(PET) blended yarns.The interlayer space of montmorillonite in the nanocomposites was characterized by means of XRD,and the adhesion of the nano-sizes to the yarns and the strength of the sized yarns were tested.The results revealed that the degree of intercalation varies with amount of Na~+-MMT in the hybrid.The acrylic copolymer/Na~+-MMT nanocomposite size can improve the adhesion of the size to cotton,resulting in an increase of strength and elongation of the sized yarn.Whereas,the PVA/Na~+-MMT nanocomposite size can enhance the adhesion to the T/C blended yarn but have little influence on the strength and elongation.