Cationic polyacrylate emulsions with different properties were prepared in lad and used as surface sizing agent, the results showed that as the increase of solid content, the properties of paper increase at first but keep constant if the solid content increase further; as the increase of the pH value of the emulsion, the strength of the paper decrease, smoothness increase, gloss and whiteness decrease, saturation and printing density increase; the increase of the size of emulsion has adverse effects on the properties of the paper, so the size should not be too large; the viscosity should not be too large and not be too low, it should be kept in a moderate level.