The invention discloses a Fischer-Tropsch synthesis simulation method and device. The method comprises the steps of determining input conditions of a Fischer-Tropsch synthesis reaction, wherein the input conditions include parameters of a fresh syngas and parameters of a first recycle gas; selecting a model and reaction parameters required by the Fischer-Tropsch synthesis reaction; determining reaction products generated after the Fischer-Tropsch synthesis reaction according to the input conditions, and the model and the reaction parameters required by the Fischer-Tropsch synthesis reaction; separating the reaction products to obtain separated products; judging whether the error between the parameters of a second recycle gas in the separated products and the parameters of the first recycle gas is smaller than a preset error limit; if not, modifying the parameters of the first recycle gas according to the parameters of the second recycle gas, conducting the Fischer-Tropsch synthesis reaction again, and judging whether the error between the parameters of the second recycle gas and the parameters of the first recycle gas is smaller than the preset error limit till the error is smaller than the error limit. The problem that existing simulation methods can not be specifically aimed at Fischer-Tropsch synthesis is solved.