Various poly(macromonomer)s of ring-opened poly(norbornene) backbone containing ring-opened poly(norbornene) derivatives in the side chain have been prepared efficiently by repeating the ring-opening metathesis polymerizations (ROMP) using well-defined molybdenum initiator of the type, Mo(CHCMe2Ph)(N-2,6-(Pr2C6H3)-Pr-i)(OR)(2) [OR = OCMe3, OCMe(CF3)(2)]. The key steps for synthesis of the macromonomer are both exclusive end-capping and quantitative esterification of hydroxy group at the polymer chain end with norbornene carboxylic acid chloride, and the use of Mo(CHCMe2Ph)N-2,6-(i)-Pr2C6H3)[OCMe(CF3)(2)](2) was found to be an effective initiator in order for this polymerization to proceed to the complete conversion. The present synthetic approach should be useful for preparing various poly (macromonorner)s containing functional groups, especially amphiphilic poly(macromonomer) architectures precisely.