Abstract: The present invention relates to a polymerization process for preparing syndiotactic polystyrenes, which comprises a step of microfluidizing in a microfluidization apparatus both a catalyst mixture consisting of a styrene monomer, a metallocene catalyst and an inert organic solvent and a cocatalyst mixture consisting of a styrene monomer, a cocatalyst and an inert organic solvent, and a step of reacting the microfluidized mixture with a catalyst and a cocatalyst in a reactor. The metallocene catalyst has a bridged structure of a complex of Group IV transition metals such as Ti, Zr, Hf etc. in the Periodic Table and a ligand having one or two cycloalkane dienyl groups such as cyclopentadienyl group, indenyl groups, fluorenyl group, and derivatives thereof. The reactor is a well stirred reactor equipped with agitating blades therein to mix the reactants well.