YSZ-based mixed potential type NH3 sensor has a good application foreground in on-board SCR (Selective Catalytic Reduction) system due to its good thermal and chemical stability. In this study, we greatly improved the NH3 sensing performance of this type of sensor to meet the detection requirement through the development of high-performance sensing electrode materials. FeVO4 was synthesized through a traditional sol-gel method and used as basis material. In order to improve the electrochemical catalytic activity, different molar ratio of metal oxides (NiO, SnO2, WO3) modified FeVO4 were prepared. The cyclic voltammetry (CV), the linear sweep voltammetry (LSV) and dc polarization (I–V) measurements were carried out to confirm the electrochemical catalytic activity of the sensing electrode materials. Eventually, the sensor attached with 20 mol.% NiO modified FeVO4-SE exhibited the highest response (−83 mV) to 100 ppm NH3 and had a low detection limit of 5 ppm. What is more, the sensor also displayed short response and recovery time, satisfying oxygen resistance and good stability over 20 days at 650 °C, indicating its potential for in-situ ammonia monitoring in industrial and automotive applications.