Abstract: At present, the study of ultrasonic thermometry based on pulse-echo technology mainly focuses on the design of ultrasonic transducer and hardware circuit system, but the study of sensitive element at high temperature is less. In this paper, several appropriate sensor materials are evaluated, through the analysis of the dispersion characteristics and reflection of ultrasound in the rod. A 1 m long and 1 mm diameter of the thoriated tungsten rod with reflection groove is used as the sensor, and a preliminary experiment is carried out on an ultrasonic thermometry platform. The results show that the use of thoriated tungsten rod as the sensor, can effectively measure the relationship between velocity and temperature at 12 ℃ to 1 600 ℃, and the error of ultrasound measured at high temperature compared with the reference value is not more than 0.68%.