The invention relates to an agent for disinfecting an intensive care unit and a preparation method. The prepared agent is prepared from the effective ingredients including Chinese wedelia herb or roots, the root of straight ladybell, square-stems, herba clerodendranthi, tender catchweed bedstraw herb, common andrographis herb, rhizomes of chlorophytum comosum, leaves of Ligustrum sinense Lour., folium eucalypti, ternate grape fern herb, clerodendrum fortunatum roots, herb of klein cinquefoil, burdock roots, cudweed herb, locust tree branches and paniculate swallowwort roots. The medicine materials selected in the agent are suitable in compatibility and are in proper proportion, the advantages of being high in bactericidal ability, high in acting speed, high in stability, low in price and the like are achieved, the agent can be widely applied to disinfecting the skin of personnel, instruments and the interior in the intensive care unit, and is free of simulation to the skin of the human body, and no residue exists after the agent is used; the agent can be easily dissolved in water, free of corrosivity, safe and free of toxic and side effects, the work efficiency of medical staff can be improved, and the agent is an ideal agent worthy of popularization.