Single-atom catalysts (SACs) play a key role in many chemical processes owing to highly desirable atom efficiency, but the challenging synthesis of these catalysts limits their commercialization and application on a large scale. Herein, we report a facile strategy to integrate atomic Pt into richly deficient MoO 3-x . The core of the experimental strategy was the fabrication and utilization of H x MoO 3-x with plasmon resonance that contained intercalated H + . The obtained catalyst was found to possess remarkable electrocatalytic activity toward the hydrogen evolution reaction that was even comparable to that of commercial Pt/C, whereas the amount of Pt used was reduced to only 10% of the amount of commercial Pt/C used. Therefore, this work not only supplies a new synthesis route to SACs but also reveals the potential relation between plasmon resonance materials and the fabrication of single-atom catalysts.