The invention relates to the field of separation of fine catalyst powders in slurry bed Fischer-Tropsch synthesis oil gas products, and discloses a Fischer-Tropsch synthesis system, and a method for separating a fine catalyst powder in a Fischer-Tropsch synthesis oil gas product. The system comprises: a slurry bed reactor used for carrying out a Fischer-Tropsch synthesis reaction, wherein a heat exchanger is arranged in the lower part of the slurry bed reactor, a heavy component filtering device is arranged in the middle part of the slurry bed reactor, and a gas-liquid-solid separation deviceis arranged in the upper part of the slurry bed reactor; and a fine catalyst powder separation device arranged outside the slurry bed reactor and communicated with the outlet of the gas-liquid separation device, wherein the fine catalyst powder separation device is used for separating the fine catalyst powder from the oil gas product generated by the Fischer-Tropsch synthesis reaction, the separated fine catalyst powder is discarded or is sent to a waste treatment device and treated, and the fine catalyst powder-removed high-temperature oil gas is sent to the downstream for heat exchange condensation and/or separation treatment. The system and the method can be used for large-scale slurry bed Fischer-Tropsch synthesis industrial production to effectively separate the fine catalyst powder in the oil gas product generated by reaction and prolong the operation time of the device.