Abstract: Fischer-Tropsch synthesis is an important chemical reaction for the synthesis of clean energy. 2-line ferri- hydrite is currently recognized as the precursor of Fe-based synthesis of Fe-based catalysts. Due to the poor thermody- namic stability of 2-line ferrihydrite,the derivation of the structural model is mainly based on X-ray diffraction results and transmission electron microscopy. However,there have been no reports on the combination of experiments and sim- ulations to study the nanoclusters of 2-line ferrihydrite. This research used a combination of experiments and simulations. Among them,the molecular simulation used the Dmol3 module and the Forceite module in Material Studio (MS for short) to optimize the structure of the unit cell and cluster model of 2-line ferrihydrite,respectively. Precipitation method was used to synthesize iron-based catalyst precursor 2-line ferrihydrite sample. The washing method was cen- trifugation and the drying method was freeze-drying. Characterization methods included X-ray diffraction analysis and infrared spectrum analysis. Based on the X-ray diffraction results of the experimentally prepared 2-line ferrihydrite,and in combination with the cell model parameters given by Michel etc,the unit cell model of 2-line ferrihydrite,spherical 2-line ferrihydrite nanocluster model with a diameter of 2． 66 nm and cubic 2-line ferrihydrite nanocluster model with a side length of 3． 22 nm were constructed. After the structure optimization of the model,the rationality of the unit cell and cluster model was verified by the simulated X-ray diffraction comparison chart,that is,the difference between the experimental and simulated diffraction peaks was controlled within 1. 0°. The results show that the peak positions of the X-ray diffraction patterns of the model obtained by the optimization of different functional structures are 35． 9° / 62． 7°(GGA / PBE) and 35. 8° / 61. 9° ( m-GGA / M06-L). Comparing the experimental values (35. 1° / 62. 0°),the differ- ence between the two calculation results is within 1． 0°,and the m-GGA / M06-L functional calculation results are clos- er to the experimental values. For the two nano-cluster models,the results obtained by fine precision calculation are the most accurate,and the two cluster models with different shapes are the optimal models. This study emphasizes the closeness of experiments and simulations. Starting from the experimental results and combining the X-ray diffraction simulation function of MS software,a reasonable unit cell and cluster model has been successfully established,which provides a basis for the study of ferrihydrite structure.