Abstract: Ablation temperature of the heat shield during the entry of Mars probe is one of the key parameters for thermal insulation structure design and aerothermal environment identification. To meet the requirements of in-orbit temperature measurement of thermal insulation layer, a method using the temperature sensor composed of a plunger type structure probe to measure stratified temperatures of the bottom and a U-shaped structure probe to measure the temperature of the back shell, together with cables and multi-channel temperature converters, was proposed. The design included the selection of thermocouple elements, the structural style and the installation mode of the temperature probe, as well as the centralized signal amplification transformation and automatic cold junction compensation. Full range calibration and special wind tunnel test verification were conducted. It is proved that, with the designed temperature sensor, the full process measurement of the ablation temperature change below 1300 ℃ can be achieved with a measurement accuracy of 0.28%. The temperature sensor has been successfully applied to China’s first Mars probe Tianwen-1. The proposed research may provide a reference for the in-orbit ablation temperature measurement for entry/re-entry of spacecraft.