In this article, Ce_0.8Gd_0.2O_1.95-based mixed potential type sensors attached with La_1-xSr_xMnO₃ (x = 0.1, 0.2, 0.3) were fabricated to detect triethylamine (TEA). The effects of different ratios Sr²⁺ on the performance of triethylamine sensors were studied, and results showed that La_0.8Sr_0.2MnO₃ had the best electrochemical catalytic activity to triethylamine, which could be proved by polarization curve and complex impedance curve. The sensor based on La_0.8Sr_0.2MnO₃ sensing electrode had the highest response value (−113 mV) towards 100 ppm triethylamine. The optimum working temperature of the sensor was 580 °C. The low detection limit was 1 ppm, and the response value to 1 ppm triethylamine was−8 mV. At the range of 1-100 ppm triethylamine, the sensitivity of the sensor based on La_0.8Sr_0.2MnO₃ sensing electrode was -59.2 mV/decade. In addition, the sensor also displayed excellent repeatability, stability during 30-day test and low cross-sensitivities towards interfering gases, e.g. methanol, methanal, acetone, ethanol and N-butanol. On the basis of the above research, the presented sensor can be considered as a potential sensor for monitoring triethylamine concentration in the atmospheric environment and microenvironment, and determining the freshness of fish.