To understand the process of DL-2-phenoxypropionic acid fine particles formation with rapid expansion of supercritical solution (RESS), it is vital to determine the solubility of DL-2-phenoxypropionic acid at different operation conditions and to detect an empirical model to correlate the solubility data. In this investigation, solubility in supercritical carbon dioxide (SC-CO2) was measured by a static method with the pressure ranged from (10 to 30) MPa and temperature from (308 to 323) K. Chrastil and its modified models have better correlation effects than the Mendez-Santiago and Teja model, especially the Adachi and Lu modified Chrastil model, provides a nearly perfect average absolute relative deviation (AARD) of 0.0532. Then, RESS was applied to prepare DL-2-phenoxypropionic acid microstructures. The effects of the extraction temperature ((308 to 328) K), extraction pressure ((10 to 30) MPa), spray distance ((10 to 30) mm), nozzle temperature ((343 to 383) K), and nozzle diameter ((0.1 to 0.4) mm) were searched on morphology and size of the microstructures. On the basis of the different experimental conditions, filaments with the diameter of (1 to 15) nm were obtained, which entwine into a mesh pattern and even are accompanied with flakes or particles in some cases. The micronization result indicates a general trend that the higher supersaturation at some operation conditions, the smaller the filaments observed.