The invention provides a room temperature solid electrolyte CO2 sensor and a preparation method thereof. The sensor comprises a CO2 sensor chip, wherein the CO2 sensor chip comprises an insulating substrate, a silver reference electrode, a solid electrolyte layer, a sensing electrode, a reference electrode lead and a sensing electrode lead, and the silver reference electrode is printed on the insulating substrate; the solid electrolyte layer is printed on an ionic solid electrolyte membrane of the insulating substrate, and covers 2/3 of the silver reference electrode, and the sensing electrode is coated on the surface of the ionic solid electrolyte membrane; the reference electrode lead is a gold wire or platinum wire bonded onto the silver reference electrode, and the sensing electrode lead is a gold wire or platinum wire bonded onto the sensing electrode. The method comprises: step 1, preparing the silver reference electrode; step 2, preparing the ionic solid electrolyte membrane; step 3, preparing the sensing electrode; step 4, preparing the sensor chip; step 5, encapsulating.