Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is an important DNA repair enzyme, which is closely related to the occurrence and development of certain diseases. Ultrasensitive and accurate detection of hOGG1 is significant for fundamental researches and clinical diagnosis. In this study, we have proposed a ratiometric electrochemical method for hOGG1 detection. Two electrochemical species, ferrocene (Fc) and hexaammineruthenium (III) chloride ([Ru(NH3)6]3+) are employed. After hOGG1 catalyzed reactions, the DNA probes on the electrode are cleaved and subsequent hybridization chain reaction is initiated. The variations of DNA molecular layer on the electrode lead to the decrease of Fc signal and increase of [Ru(NH3)6]3+ signal. By calculating corresponding ratios of the electrochemical responses, a wide detectable range from 0.002 to 10 U mL−1 and a low limit of detection (0.0008 U mL−1) are achieved. This approach exhibits excellent sensitivity, accuracy, and stability, which has great potential utility in biomedical researches and clinical diagnosis. Keywords: Ratiometric assay, Human 8-oxoguanine DNA glycosylase, Hybridization chain reaction, Ferrocene, Hexaammineruthenium (III) chloride