In this report, we designed a water-soluble hyperstar polymer that contained hyperbranched polytriazole as the core and dangling linear poly(ethylene oxide)s (PEO) as the arms for use as template to synthesize gold nanoparticle. The hyperbranched polymer that was synthesized from the chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization of a tetrafunctional AB(3) monomer showed low-dispersity structure, tunable sizes, and consequently produced hyperstar polymers with high density of PEO dangling arms at periphery. Loading HAuCl4 precursor at varied molar ratios to the triazole units in the core directly changed the size of Au nanoparticles after reduction by NaBH4, exhibiting different intensities in X-ray diffraction spectroscopy. The obtained Au nanoparticles were further investigated as co-catalysts for hydrogen evolution reaction when hybridized with molybdenum disulfide (MoS2) nanosheets, showing enhanced electrocatalytic activity.