Abstract Developing efficient peroxidase‐like nanozymes to surpass natural enzymes remains a significant challenge. Herein, an amorphous RuO 2 nanozyme with peroxidase‐like activity is synthesized for activating H 2 O 2 with a specific activity of 1492.52 U mg −1 , outperforming the crystalline RuO 2 nanozymes by a factor of 22 and far superior to natural peroxidases. Amorphous RuO 2 nanozymes with long‐range disordered atomic arrangements can effectively elongate the O─O bonds in H 2 O 2 . Abundant oxygen vacancies in amorphous RuO 2 nanozymes lead to an upshift of the d ‐band center, enhancing the exceptional adsorption strength of H 2 O 2 , which improve the electron transfer efficiency and ensure superior peroxidase‐like activity. Accordingly, a nanozyme‐linked immunosorbent assay is developed for the precise and sensitive detection of prostate‐specific antigens with a detection limit as low as 0.52 pg mL −1 . This study introduces a simple approach for developing high‐performance peroxidase‐like nanozymes to improve the analytical performances of prostate‐specific antigens in clinical diagnostics.