Accurately monitoring heat flux distribution can enhance the service stability of aeroengine hot-end components. The extreme environmental temperature and fast heat transfer between high-speed load and hot components propose serious requirements for heat flux sensors, including high-temperature resistance and fast response. This article fabricates the fast response thin film heat flux sensor based on the transverse thermoelectric (TTE) effect of La _1-x Ca _x MnO ₃ (LCMO). The TTE heat flux sensor shows excellent high-temperature resistance at 1000°C. After high-temperature heat treatment for 1 h, the performance of the sensor is improved due to the optimization of the crystal quality and biaxial texture of the LCMO thin film, as well as the reduction of resistance. The sensitivity increases from 7.39 μV/(kW/m ² ) to 7.79 μV/(kW/m ² ), and the response time reduces from 58 ns to 42 ns. Then, the performance of the thin film heat flux sensor shows little changes after completing high-temperature heat treatment for up to 7 hours at 1000°C. The TTE heat flux sensor can show a satisfied response in a high-temperature environment at 1000°C, with a sensitivity of 1.18 μV/(kW/m ² ) without the consideration of laser absorption. The TTE heat flux sensor exhibits stable high-temperature resistance at 1000°C and can operate normally at 1000°C, indicating its potential in fast heat flux measurement for harsh environments.