The invention discloses a cellulose fiber for preventing X-ray radiation and a preparation method of the cellulose fiber; barium sulfate powder with grain size not greater than 3 microns is processed in organic dispersing mediums miscible with water to prepare barium sulfate emulsion slurry; then the barium sulfate emulsion slurry is added to yellowed and dissolved viscose solution according to content of barium sulfate being 10-30% of alpha cellulose by weight percentage to mix uniformly, and then is span and formed through spinning coagulation bath, drafted and post-processed to obtain the cellulose fiber for preventing X-ray radiation. According to the invention, X-ray screening agent of barium sulfate has good dispersity in viscose fibers; less barium sulfate is lost when spinning and forming; prepared fibers have the advantages of good physical and mechanical properties, textile processing property and wearability, and further have the advantages of high X-ray screening ratio and good durability; and the screening ratio for X-rays is not less than 65%. The fiber can be widely applied to industries for manufacturing dresses of workers contacting X-rays in long term, and non-woven fabrics.