The invention relates to the field of online updating of Fischer-Tropsch catalysts, and discloses an online updating apparatus and an online updating method for a slurry bed Fischer-Tropsch synthesisreactor catalyst. The apparatus comprises a fluidized bed activation reactor, a cyclone separator, a storage tank, a heater, a slurry bed Fischer-Tropsch synthesis reactor, a gas-liquid-solid separator, and a liquid-solid treatment unit communicated to the slurry bed Fischer-Tropsch synthesis reactor and the gas-liquid-solid separator, wherein the fluidized bed activation reactor, the cyclone separator, the storage tank, the heater, the slurry bed Fischer-Tropsch synthesis reactor and the gas-liquid-solid separator are sequentially communicated, the fluidized bed activation reactor is used formaking a fresh Fischer-Tropsch catalyst contact a reducing gas so as to activate the catalyst, and the liquid-solid treatment unit is used for carrying out solid waste and waste catalyst separation on first residue wax and second residue wax. According to the present invention, by adopting the apparatus, the Fischer-Tropsch catalyst activation cost and the residue wax treatment cost can be reduced, the start-up preparation time of the apparatus can be shortened, the catalyst in the slurry bed Fischer-Tropsch synthesis reactor can be updated day by day, the residue wax treatment is simple andconvenient, the separation efficiency is high, and the stable operation of the apparatus is ensured to the greatest extent.