Here, the porous SnO 2 /Zn 2 SnO 4 sensing electrode material prepared by facile hydrothermal method was applied to fabricate the mixed-potential-type gas sensor based on yttrium-stabilized zirconia (8 mol% Y 2 O 3 -doped ZrO 2 ) solid electrolyte plane substrate for effectively detecting acetylene (C 2 H 2 ) at 700 °C. In terms of the sensing characteristics of the C 2 H 2 gas sensor, the response value toward 100 ppm C 2 H 2 was -82.3 mV, and the detection limit of C 2 H 2 was lowered to 500 ppb. The ΔV of the sensing device varied piecewise linearly with the logarithm of C 2 H 2 concentration gradient range of 0.5–2 and 5–1000 ppm, with sensitivities of -12 and −56 mV/decade, respectively. In addition, the sensor exhibited good humidity stability, long stability, and selectivity to C 2 H 2 at 700 °C. More interestingly, after high-temperature measurement (700 °C) for 20 consecutive days, the sensor continued to present good response transients, sensitivity, and reproducibility to C 2 H 2 . Furthermore, the sensing mechanism of the mixed-potential-type sensor was verified by measuring the polarization curves and complex impedance curves.