New thermoplastic norbornene polymers containing ester groups were prepared by vinylic polymerization of norbornene-carboxylic acid esters by Pd(Ⅱ)-based catalysts. The monomers were obtained by Diels-Alder reaction of cyclopentadiene with acrylic acid esters(methyl and butyl) as mixtures of endo/exo (ratio 40/60)-isomers and were converted to polymers in 60%~70% conversion. The endo- isomer was less reactive than the exo -isomer. To obtain higher molecular weight the more reactive pure exo- isomer was prepared and polymerized with the Pd(Ⅱ)-catalysts, tetrakis(acetonitrile)Pd(Ⅱ) bis(tetrafluoroborate) and ( η 3-allyl)Pd(Ⅱ)SbF 6, in high conversion. These polymers showed high glass transition temperatures, high transparency and good solubility in common solvents. The monomers were obtained by Diels-Alder reaction of cyclopentadiene with acrylic acid esters (methyl and butyl) as mixtures of endo / exo (ratio 40/60) -isomers and were converted to polymers in 60% to 70% conversion. The endo- isomer was less reactive than the exo-isomer. To obtain higher molecular weight the more reactive pure exo- isomer was prepared and polymerized with the Pd (Ⅱ) -catalysts, tetrakis (acetonitrile) Pd (Ⅱ) bis (tetrafluoroborate) and (η 3 -allyl) Pd high transparency and good solubility in common solvents.