In order to develop cotton fabric underwear with the health care function, the cotton fiber was modified with the collagen (CMCF) using periodate oxidation method. The aldehyde groups on the glucose chains of the oxidized cotton cellulose were reacted with the amino groups of collagen to obtain the CMCF, and the oxidized cellulose was crosslinked with collagen in aqueous acetic acid media. The effects of collagen concentration, treatment time, reaction temperature, pH value of solution and periodate concentration on the amount of collagen crosslinked on cotton fiber were respectively discussed, and the optimal reaction technology was obtained. XPS characterization of the modified cotton fiber showed a characteristic peak about 400.0–405.0 eV corresponding to collagen, which indicated that the collagen was combined on the surface of cotton fiber. The mechanical properties of the collagen modified cotton fiber were improved. The resulting CMCF is a new natural ecological fiber and has the extensive application as a carrier for the controlled release of drugs.