Rectorite (REC), one kind of layered silicates, has been applied to polymers to improve their properties. The sodium alginate (SA) layered silicate is a new option to modify the properties of polysaccharides. In this article, SA was modified by Na+-rectorite (Na+REC). The chemical structures and microstructures of Na+REC and Na+REC modified SA (SA/Na+REC) were analyzed by using Fourier transform infrared spectrometer and X-ray diffraction. The morphologies of SA/Na+REC composites were observed by using scanning electron microscopy and transmission electron microscopy. The mechanical and anti-ultraviolet properties as well as thermal properties of SA/Na+REC composites were investigated. The results show that the properties of pure SA film can be improved by the addition of Na+REC, and SA/Na+REC composite containing 2 wt % Na+REC has the best intercalation effect and optimum comprehensive properties among the prepared composites in this article. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1235-1240, 2009