The invention discloses an oxidation-sulfonation 
starch water 
reducing agent preparation method, which comprises: adding water to a reaction kettle, adding 20-40% of 
corn starch while stirring, adjusting the pH value of the 
starch milk to 9-11 with an alkaline substance, adding an 
oxidizing agent while stirring, continuously carrying out the stirring reaction for 3-5 h at a temperature of 30-45 DEG C, adjusting with an acid to achieve a 
neutral state, filtering, and 
drying to obtain oxidation 
starch; and adding an 
organic solvent to a reaction kettle, adding 10-15% of the oxidation starch while stirring, controlling the temperature at 0-60 DEG C, slowly adding an acidic substance and 
organic solvent mixture in a dropwise manner, stirring for 1-2 h, terminating the reaction, filtering, and 
drying so as to obtain the oxidation-sulfonation starch. According to the present invention, the process of the preparation method is simple; after the product is added to 
cement, the 
cement slurry has good fluidity and good retardability; after the product is added to 
mortar, the advantages of fluidity increasing, 
water consumption reducing, 
compressive strength increasing and bending strength increasing can be provided; and after the product is added to concrete, the 
slump of the concrete can be increased, and the strength is improved.