The invention discloses a combustible gas and smog leakage reminding device. The combustible gas and smog leakage reminding device is characterized by comprising a 9V direct-current electrical source, a gas detection circuit, a critical value sampling circuit, an astable multivibrator circuit and an audio output circuit. The gas detection circuit is composed of a gas sensor QM and a resistor R1, and the selected model of the gas sensor QM is QM-N6. The astable multivibrator circuit and the audio output circuit are composed of a time-base circuit IC1, a resistor R2, a resistor R3, a capacitor C1 and a piezoelectric ceramic piece HA, and the selected model of the time-base circuit IC1 is NE555. The combustible gas and smog leakage reminding device is a gas leakage warning device with the gas sensor used as a detecting element, the device is suitable for detecting leakage of volatile gas such as natural gas, coal gas, gasoline, carbon monoxide, hydrogen, alkanes and alcohol, and timely detection warning can be conducted on smog formed by fires of wood, paper, woolens, rubber products, plastic products and the like.