A thermo-chemical cross-linking preparation method of silicone carbide fiber and a cross-linking device relates to a silicone carbide fiber, in particular to a method that the thermo-chemical cross-linking of organometallic compounds is used for the preparation of silicone carbide fiber and the cross-linking device of the method, which provides a thermo-chemical cross-linking preparation method of silicone carbide fiber and a cross-linking device of the method and provided with a quartz glass tube, an inlet tube, an outlet tube, a sealing steel sleeve, a gas flow control valve, a heating coil and a quartz boat. The heating coil is arranged outside of the quartz glass tube. The inlet and outlet tubes are respectively linked on both ends of the quartz glass tube through the sealing steel sleeve, and the quartz is disposed inside the quartz glass tube. The PCS and a cross-linking agent are dissolved in the trtrahydrofuran, and the slurry is produced. The slurry is in ageing and with the dry-spinning, thus the precursor fiber is produced. The precursor disposed into the quartz is then disposed into the cross-linking device for the thermo-chemical cross-linking. The PCS cross-linking fiber is obtained, which is then disposed into a high-temperature furnace for pyrolysis and sintering. Therefore, the silicon carbide fiber is produced.