A polyurethane(PU)/clay nanocomposite based on poly(tetramethylene glycol) (PTMG), trifunctional polyisocyanate and montmoirllonite was synthesized. It was found that montmorillonite exchanged with long chain onium ions are easily solvated by PTMG. After the polyol dispersed clay was cured with polyisocyanate, tensile modulus and tensile strength as well as the tensile strain was increased. And, the cured film was transparent. The structure/property relationships of these filled polyurethane elastomers were investigated.