A new kind of soluble structure-ordered ladder-like polysilsesquioxane with reactive side-chain 2-(-4-chloromethyl phenyl) ethyl groups (L) was first synthesized by stepwise coupling polymerization. The monomer, 2-(4-chloromethyl phenyl) ethyltrichlorosilane (M), was synthesized succesfully by hydrosilylation reaction with dicyclopentadienylplatinum(II) chloride (Cp2PtCl2) catalyst. Monomer and polymer structures were characterized by FT-IR, 1H-NMR, 13C-NMR, 29Si-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vapor pressure osmometry (VPO) and X-ray diffraction (XRD). This novel reactive ladder-like polymer has promise potential applications as initiator for atom transfer radical polymerization, and as precursor for a variety of advanced functional polymers. Copyright © 2001 John Wiley & Sons, Ltd.