Abstract: In order to realize the heat transfer printing of cotton fabric, the idea of “bridge-linking” was put forward and a bridge-linking agent named FY-1 was prepared. The feasibility of bridge theory was proved by the example: heat transfer printing was performed on the cotton fabric which had been pretreated by FY-1, with C.I. disperse red 60. The bridge mechanism was analyzed by using physical methods such as optical microscope, transmission electron microscope. It seems there are three steps in heat transfer printing of cotton fabric: the bridge-linking agent enters into the fiber by the affinity and penetrating power, distributing dye-sites for disperse dye in the micropore; the bridge-linking agent can swell fiber at heat transfer printing temperature with the help of its thermo-swellability; disperse dyes sublimate at heat transfer printing temperature and dye on fiber through the force between molecules.