Manganese oxides are a family of microporous transition metal oxides that can form mixed-valent semiconducting octahedral molecular sieves (OMS) with tunnel structures of various sizes. Among these, β-MnO₂(pyrolusite), an ordered 1×1 tunnel structure shared with MnO₆octahedral chains, has been extensively used as a cathode material, sensors, magnetic material, and catalyst. Although many studies have been devoted to the synthetic research of β-MnO₂, the large-scale preparation of 1-D β-MnO₂nanomaterials through a facile and cost-effective approach has not been fully developed. Herein, we introduce a simple one-step reflux process at atmospheric pressure for preparing scales of β-MnO₂nanorods. Single-crystalline β-MnO₂nanorods were successfully synthesized through facile reflux treatment of KMnO₄and MnSO₄ in HNO₃ solution. TEM and SEM images show that the synthesized β-MnO₂ nanorods exhibited diameters of 20–50 nm, and lengths that ranged from approximately 0.5 to 2.0 μm with decreasing HNO₃ concentrations from 0.8 to 0.1 mol/L. The prepared β-MnO₂ nanorods showed excellent catalytic activity for the degradation of methylene blue dye by a Fenton-like reaction. Because of its simple manipulation and high yield, this synthetic process may have potential applications in environmental technology.