Microspheres of poly(p-oxycinnamoyl) (POC) were obtained by the polymerization of (E )-4- acetoxycinnamic acid in aromatic solvent at 320degree and a concentration of 1.5% without stirring via liquid-liquid phase separation of oligomers. In contrast to this, rod-like crystals were formed under shearing with more than 700 rpm. The obtained rod-like crystals were 10-15 um in length and 1.0-1.5 um in width having many thorns on the surface. The critical stirring speed for the onset of Taylor vortices was in agreement with 700 rpm and the crystallization of oligomers was hydrodynamically induced by the generation of Taylor vortices affording the rod-like crystals. Stirring influenced the morphology of POC significantly and this work provided a new procedure for the fabrication of fine fibers of intractable aromatic polymers.