Abstract: Poly(3-hexylthiophene) (P3HT) used in organic field effect transistors, polymer solar cells and so on has received continuous attentions. The conformation of individual chains and the degree of the π-π stacking are considered to be the important factors to determine the device performance. As the solution-processing material, there is no doubt that the solvent properties such as solubility and boiling-point affect the structures of P3HT solid film. However, there is no consistent conclusion that which factor makes the main contribution. In this work, by using Fluorescence correlation spectroscopy, UV-Vis spectroscopy, and reflection-absorption infrared spectroscopy, the effect of the solvent properties on the P3HT lamellar structure in the solid film is investigated. Four different solvents, carbon disulfide, chloroform, toluene and chlorobenzene, were employed. P3HT molecules show more extended conformation in the good solvents of carbon disulfide and chlorobenzene, which show higher solubility to P3HT, compared to the poor solvents of toluene and chloroform. However, in the solid state, the solvent boiling-point plays the important role in the lamellar structure. Firstly, the better backbone planarity comes from the film deposited from the solution in which the solvent has higher boiling-point. Furthermore, the π-π interaction between adjacent molecular chains is also improved with the increasing of solvent boiling-point. Besides, the molecular orientation is also affected by the solvent boiling-point. The prolonged solvent evaporation time attributed from the higher boiling-point of toluene and chlorobenzene prefers to induce the "edge-on" orientation of P3HT, whereas the "face-on" orientation exists in the film spin-coated from carbon disulfide and chloroform with lower boiling-points.