Abstract: To meet the sizing needs of high-count and high-density pure cotton fabrics,a new acrylic size with low backstaining and high strength of size film was synthesized through studying the nature and characteristics of acrylics monomers,analyzing and selecting suitable monomers,and determining the best proportion of soft monomer to hard monomer.IR study showed that all the monomers participate in the polymerization.Laser diffractometry illustrated that the diameter of the new size particulate is 4.9μm,which is very suitable for penetrating into and sticking to cotton yarns,this is why the new acrylic size was performance as sizing agent.And it was proven by sizing experiments.