The invention discloses a buck principle based ignition and flame-detection circuit and a fuel gas wall-hanging stove adopting the circuit. The buck principle based ignition and flame-detection circuit comprises a controller and an ignition module, wherein the ignition module comprises a voltage-reducing and detecting unit which is connected to an external direct-current power supply. Buck circuitinductance and load are charged together, and power of a bucket circuit is greater than boost, and therefore, inductance and a rectified circuit size are smaller than boost, and the cost can be saved; a high-frequency transformer sampling circuit is used to replace the original resistance type sampling circuit, so that safety is higher; a high-frequency transformer is adopted to replace inductance in an existing circuit, so that the inductance howling problem is eliminated; and feedback voltage of the transformer is adopted to effectively isolate high voltage of an ignition power supply froma controller chip, so that safety of the circuit is improved.