The invention discloses a modified gelatin fiber. Characteristic absorption peaks appear nearby 3290 cm<->, 1628 cm<->, 1527 cm<-> and 1230 cm<-> in the infrared spectrum of the gelatin fiber. The gelatin fiber is prepared by dissolving gelatin in a solvent for swelling and then to mixing with a cross-linking agent, then adding a mixed material obtained in the previous step into spinning equipment so as to obtain nascent fiber, and subjecting the nascent fiber to aftertreatment. According to the invention, transglutaminase is used as the cross-linking agent which is safe to use; and the prepared gelatin fiber has good stability in water and improved mechanical properties and is applicable to the fields of biology and medicine.