A novel hyperbranched azo-polymer was prepared by a ruthenium-based catalyst RuCl2(PCy3)(SIMes)(CHPh) using acyclic diene metathesis (ADMET) polymerization of an AB(2) monomer, 4-undecylenyloxycarbonyl-4'-[bis(2-ethyl acrylate)amino]azobenzene, which was synthesized from the esterification reaction between N,N-bis(2-ethyl acrylate)aniline and 4-carboxy-4'-[bis(2-ethyl acrylate)amino] azobenzene. The monomer and polymer were characterized by mass spectrometer, elemental analysis, IR, UV-vis, and NMR measurements. The produced polymers have molecular weights within 5.83 and 23.5 kDa, and their polydispersity indices range from 1.73 to 1.86 by multiangle laser light scattering-gel permeation chromatography (MALLS-GPC). The hyperbranched azo-polymer underwent efficient photoisomerization from trans to cis as observation in UV-vis spectroscopy. The degree of branching (DB) was determined by using H-1 NMR spectroscopy and the values ranged from 0.57 to 0.45.