A cathodic electro-Fenton system capable of efficiently treating tetracycline hydrochloride (TCH) in water was built by preparing a manganese oxide doped nano-graphite (Nano-G) electrode (MnOx/Nano-G electrode) and using it as the working electrode using the sol-gel and hot-pressing methods. The MnOx/Nano-G electrode was characterized by SEM, XRD, XPS, cyclic voltammetry and electrochemical impedance tests. The results demonstrated that MnOx doping could significantly improve the electrical conductivity, electrochemical stability and electrochemical activity of the Nano-G electrode, thereby improving the efficacy of cathodic electro-Fenton treatment of TCH. The best TCH degradation effect was achieved at an initial TCH concentration of 20 mg?L-1, current density of 30 mA?cm-2, initial pH of 5.0 and electrode plate distance of 10 mm. After 60 minutes, 59.27 percent of TCH had been effectively removed, and the TCH degradation efficiency had increased by 18.70 percent when compared to the unmodified Nano-G electrode. Furthermore, the cathodic electro-Fenton system of MnOx/Nano-G had a significantly higher treatment efficiency than the conventional RuO2-IrO2/Ti cathode and titanium mesh cathode. Results indicate that the cathodic electro-Fenton system of MnOx/Nano-G is an efficient and promising technology for TCH treatment.