Isotactic polystyrene (iPS) was rapidly crystallized by cooling a solution in the lat ge molecule solvent octadecyl benzoate at a rate of 10 degrees C/min. The crystallinity is near 0.7 measured by the wide-angle X-ray diffraction method, which is much higher than that for iPS samples crystallized by solution crystallization in a small molecule solvent, solvent-induced crystallization, high temperature annealing, and their combinations. Fourier Transform infrared spectroscopic shows that the iPS chains in the concentrated solution in octadecyl benzoate had a highly ordered 3(1) helical conformation. It is presumed that the molar size of solvent exerted a large influence on the formation of helical conformation and, thereby, on the crystallization rate of iPS in the solution.