The present invention relates to the technical field of nanometer 
selenium hydrosols, particularly to a nanometer 
selenium hydrosol having 
antitumor activity, a preparation method, a preservation method and applications thereof, wherein the 
hydrosol at least contains nanometer 
selenium with a concentration of 0.5-5.0 mmol / L, and 
Coriolus versicolor polysaccharide protein with a concentration of 100.0-600.0 mg / L. The preparation method at least comprises: S01, adding a solution containing selenium ions and / or selenous ions to a 
Coriolus versicolor polysaccharide protein aqueous solution; S02, adding a 
reducing agent solution to the 
mixed solution obtained in the step S01 in a dropwise manner, and shaking; and S03, carrying out volume metering on the product obtained after the reducing reaction, and carrying out 
dialysis treatment. According to the present invention, the 
hydrosol is stable at a temperature of 2-10 DEG C; and the 
Coriolus versicolor polysaccharide protein has the hydrophilic hydroxyl and the hydrophilic amino, and the two groups can enhance the affinity between the nanometer selenium and the 
cancer cells, and can improve the uptake on the nanometer selenium by 
tumor cells so as to achieve the whole 
treatment effect of medication dosage reducing, 
treatment effect improving and less toxic-
side effect, such that the effective scheme is provided for the 
combination chemotherapy of cancers in the clinic.