Abstract: Because of the regularity of the nanowire and its large ratio of length to diameter, it can greatly improve the electron mobility along the nanowire growth direction, therefore nanowire becomes the research focus in the photoelectric polymer field. External field can influence the order degree of polymer chain. In order to investigate the effect of the external field on the order degree of poly(3-hexylthiophene) (P3HT) chains in detail, the influence of the rotating shearing field, the ultraviolet radiation, and the ultrasonic treatment field on the crystallization behavior of the P3HT/mixed solvent (CHCl₃-CH₂Cl₂, V_CHCl3/V_CH2Cl2=1/2) was investigated by using UV-Vis spectroscopy and AFM. In addition, the "memory effect" of P3HT solution crystallization was studied. The in-situ UV-Vis characterization for the effect of the rotating shearing field on the structure is performed on the home-made instrument. Under the rotating shear field, ultraviolet irradiation and ultrasonic treatment, the degree of crystallization and aggregation of P3HT solutions mixed solvents are different. The degree of crystallization of P3HT is significantly improved by rotating at 1 500 r/min for 24 h, and under ultraviolet light of 254 nm and 365 nm for 20 min. The crystallinity of P3HT solution is also improved. The external fields have not changed the H aggregation of the nanowires. The crystal microstructure and morphology change depends on different initial states of the P3HT solution.