Due to excellent performances such as superior catalytic activity, high stability and convenient synthesis, the artificial enzymes with high efficiency gain significant attention in both academic and industrial research. However, many artificial enzymes face some challenges including low sensitivity, poor selectivity and relatively poor stability. In this work, we successfully employed aminopropyl-modified dendritic porous silica nanospheres (DPSNs-NH₂) as a carrier to fabricate a series of robust and effective nanocatalysts (DPSNs-NH₂@Pt) with many small Pt nanoparticles (NPs) uniformly loaded on the surface of center-radial large pores. Among DPSNs-NH₂@Pt nanocatalysts with tunable sizes of Pt NPs, DPSNs-NH₂@Pt with Pt NPs size of ca. 2.5 nm exhibited excellent peroxidase-like catalytic activity and selectivity as an artificial enzyme in model reaction of 3,5,3′,5′-tetramethylbenzidine (TMB) oxidation, with reaction rate of 8.3 × 10⁻⁵ mol L⁻¹ s⁻¹ g⁻¹ under the optimal catalytic conditions (T = 55 °C, pH = 1.5). Moreover, it also showed stable catalytic activity even after ultrasonic treatment at 600 W for 50 min, which should be ascribed to structural stability of DPSNs-NH₂@Pt. The obtained results should provide some insights for the design and fabrication of the supported catalysts as artificial enzymes.