In this paper, YSZ-based mixed potential SO₂sensor with ZnGa₂O₄and Pt electrodes was developed and the effect of the continuous testing and aging process on the sensing characteristics was discussed. The results showed that with this process the response of the sensor to SO₂performed an opposite direction to that in the sensor's initial state. The reason might be that the PtS produced at the Pt electrode increased the electrochemical catalytic activity of the Pt electrode, leading to the mixed potential of the Pt electrode higher than that of the ZnGa₂O₄electrode. XPS and EDS results proved that a lot of Pt²⁺and S^2-were produced at Pt electrode after this process. Moreover, vulcanized sensor also performed similar sensing properties to the above aging sensor, which indicated that the produced PtS should be the reason that the sensor performed reverse deflection on sensing properties. In addition, the sensor after sulfuration can detect 0.05-500 ppm SO₂with the sensitivity being 5 mV/decade to 0.05-1 ppm and 41 mV/decade to 1-500 ppm. The sensor also had a reliable stability during the continuous measurement.