Abstract: The toughness and mechanical strength of epoxy resin surface size were improved by adding some nanoTiO2 to epoxy resin emulsion dispersed with ultrasonic method. Process parameters were varied systematically with the aim of achieving an optimum dispersion process. The results showed that an optimum dispersion with epoxy resin particle size of 169 μｍ was achieved when the dispersion time was 30 min, the temperature of epoxy resin was 50 ℃, the ultrasonic amplitude was 100 %, the mass fraction of epoxy resin was 60%, and 3% nanoTiO2 was incorporated. And the opacity, storage modulus and loss factor of modified epoxy resin increased obviously while tend decreased slightly. Compared with unmodified epoxy resin, modified epoxy resin surface sizing agent had a clear positive effect on CD tensile strength, pickstrength and folding strength, where as a little negative influence on stiffness.