Preparation method of selenized platymonas exopolysaccharides and selenized platymonas exopolysaccharides

The invention discloses selenized platymonas exopolysaccharides and a preparation method thereof. The preparation method of the selenized platymonas exopolysaccharides comprises the following steps: by taking platymonas as a raw material, extracting platymonas exopolysaccharides; adding the platymonas exopolysaccharides into a nitric acid solution, and carrying out dissolution; adding BaCl2 and NaSeO3 into the solution after dissolution, and carrying out dissolution so as to obtain a reaction liquid; carrying out a reaction on the reaction liquid for 6-10 hours under conditions of 50-70 DEG C, ultrasonic frequency of 35-45KHz and ultrasonic power of 60-80W so as to obtain a half-finished product solution; adding the half-finished product solution into a saturated NaHCO3 solution, adjusting the pH value to 7, putting the solution into a dialysis bag of which the molecular weight cut-off is 800-1200, carrying out dialysis for 24 hours or greater once or greater, and stopping dialysis till the liquid outside an