Preparing method for cationic rosin size

The invention provides a preparing method for cationic rosin size. The preparing method comprises the following steps that rosin and intensified rosin are added in a reaction kettle and heated to a molten state; then, an emulsifying agent is added into the reaction kettle and fully stirred; then, hot deionized water is dropwise added into the reaction kettle and fully stirred, and rosin pre-emulsion is obtained; the prepared rosin pre-emulsion is homogenized through a homogenizing machine, aluminum salt is added, a proper amount of cold deionized water is added to regulate the solid content to be 32%, discharging is carried out, and the cationic rosin size is obtained. The cationic rosin size prepared with the preparing method is fine in particle size and high in whiteness and has little foam and higher stability compared with market products, and thus the preparing method for the cationic rosin size has good market prospects.