Nano titanium dioxide (TiO2) sols were prepared by sol-gel method with tetrabutyl orthotitanate (TBOT) as precursors, citric acid (CA) as inhibitors. Ultraviolet resistant capacity of finished cotton fabrics are greatly improved with good wrinkle-resistance, whiteness and tensile strength as well. The optimum molar ratio for preparing nano-TiO2 sols in this study is n[C2H5OH] : n[H2O] : n[CA] : n[HCl] : n[TOBT] = 20 : 6 : 1.2 : 0.025 : 1, at ambient temperature. Particle size distribution analysis of the sol reveals that the curve is right tailed with an average diameter of 72.8 nm. Factors affecting the performance of finished cotton fabrics by TiO2 sols, such as concentration of sodium hypophosphite (SHP), triethanolamine (TEA) in finishing bath, curing temperatures and time lengths were investigated by orthogonal experiments. The optimum finishing results can be obtained with 3% SHP, 3% TEA, curing at 165 degrees C for 3 min. Aggregated nano-TiO2 particles on surfaces of finished cotton fibers both washed and unwashed were investigated by high resolution cold field emission scanning electron microscope and energy dispersive X-ray spectrometer. Esterification crosslinking between CA and cotton fibers were also demonstrated through infrared spectra. After a five-time's wash, ultraviolet protection factor of finished cotton fabrics with nano-TiO2 sols is up to 117.42 and dry crease recovery angles increase by 30.2 degrees with slightly improved whiteness, while the breaking strength decreases by 18.8%. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2090-2098, 2011