Enzymatic biofuel cell (EBFC)-based self-powered biosensors could offer significant advantages: no requirement for an external power source, simple instruments, and easy miniaturization. However, they also suffered from the limitations of lower sensitivity or specific targets. In this study, a self-powered biosensor for the ultrasensitive and selective detection of single nucleotide polymorphisms (SNPs) produced by combining the toehold-mediated strand displacement reaction (SDR) and DNA hybridization chain reaction (HCR) was proposed. Herein, the capture probe (CP) with an external toehold was designed to switch on the sensing system. In the presence of target sequence, both SDR and DNA HCR reaction would happen to produce a long double-helix chain. Because of the electrostatic interaction between [Ru(NH3)6]3+ and the double-helix chain described above, the open circuit voltage ( EOCV) of the as-proposed biosensor was significantly elevated, thus realizing the detection of SNPs. Overall, in this work, an ingeniously constructed self-powered biosensor for the detection of SNPs was created by integrating EBFCs with a DNA amplification strategy. Furthermore, the as-proposed self-powered biosensor not only showed prominent specificity to distinguish the p53 gene fragment from random sequences (e.g., single-base mutant sequences) but exhibited excellent sensitivity with the detection limit of 20 aM. More importantly, the results obtained from the real cell lysate sample have laid a strong foundation for disease diagnostics and, potentially, as a powerful tool for even more fields.