description the process for the production of cationic starch having remarkable advantages as a dry strength agent according to the present invention and the application thereof as a dry strengthening agent will be described hereinbelow gelatinization is effected in accordance with conventional procedure by adding water to starch to prepare a slurry mixture and further adding alkali to the slurry mixture powdery or liquid quaternary aminoalkylated starch is commercially available such quaternary aminoalkylated starch has the following general formula str2 wherein r 1 is c 1 c 4 alkylene group r 2 r 3 or r 4 is c 1 c 4 alkyl group x is hydrogen atom or hydroxyl group and a is acid residue in the present invention either such commercially available quaternary aminoalkylated starch may be used as the starting material or such starch may originally be prepared in accordance with such a manner that starch is gelatinized in alkaline condition then 2 3 epoxypropyltrimethylammonium chloride or 3 chloro 2 hydroxypropyltrimethylammonium chloride is added thereto and the resulting mixture is warmed at a temperature of around 60 u00b0 c to react the same this reaction may also be carried out at the same time or after the undermentioned cyanoethylation when the aforesaid gelatinized starch liquid or quaternary aminoalkylated gelatinized starch liquid is mixed with a prescribed amount of acrylonitrile in strong alkaline condition and the mixture is reacted with stirring each of the corresponding cyanoethylates can be obtained the cyanoethylating reaction is very rapid in strong alkaline conditions i.