With the rapid development of modern industries, the high-temperature piezoelectric sensors that can work in extreme environments are in great demand. In this work, langasite (La₃Ga₅SiO${}_{14}$, LGS), as a high-temperature piezoelectric crystal with stable electro-elastic performance, is used as core element, and air and porous Al₂O₃ are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission (AE) sensors. The detection sensitivities at 25–500^∘C are analyzed by the ball falling test and Hsu–Nielsen experiment. Under the condition of 25–500^∘C, the received amplitude signals by both sensors are maintained above 90$$dB stimulated by the ZrO₂ ceramic ball dropping. In the Hsu–Nielsen experiment, as the temperature rising from 25^∘C to 500^∘C, the signal amplitude of sensor with air backing layer decays from 447$$mV to 365$$mV, while the signal amplitude varies from 270$$mV to 203$$mV for the sensor with porous Al₂O₃ backing layer. Significantly, compared with the bandwidth of the air-backing sensor (37–183$$kHz), the sensor with porous Al₂O₃ backing layer broadens bandwidth to 28–273$$kHz. These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500^∘C. Therefore, piezoelectric AE sensor based on LGS has great potential application in the field of high-temperature structural health monitoring.