The invention discloses a disinfectant used for a radiation room and a preparation method thereof and belongs to the technical field of medical disinfection. The disinfectant disclosed by the invention is prepared from the following raw materials: povidone iodine, fucoidan sulfate, peroxyacetic acid, cichorium endivia, aristolochia, lavender, cactus, aloe, cassia tora, astragalus, oriental wormwood, fritillaria cirrhosa, chrysanthemum, selenium-enriched tea, liquorice and silver nitrate. The disinfection method disclosed by the invention has the advantages that detection rate on bacteria such as bacillus licheniformis is reduced year by year, CT room infection rate is 10.9-12.1%, blood vessel-related infection rate is 3.1-3.9%, respiratory tract infection rate is 9.4-10.9%, viral infection rate is 0.2-0.4%, skin and mucous injury severity is 1.07-1.19%, infection can not be caused, and cost is low.