Abstract: This paper designs an ultrasonic temperature measurement system for liquid media to achieve rapid and high-precision measurement of liquid temperature. An optimized threshold comparison method is proposed. To more precisely define the end moment of ultrasonic wave propagation, the pulse width of the signal is determined based on the conventional threshold comparison method. At the same time, the TDC structure design based on the tap delay chain is utilized to improve the resolution of time measurement, and the relationship between ultrasonic wave propagation speed and liquid temperature is established to achieve accurate temperature measurement. According to the experimental findings, the system is capable of measuring temperature at a resolution of 0.001 ℃ by reaching the time measurement resolution of 10-12 s, with an average measurement error of 0.008×10-9 s. It also has a faster response speed and a higher sensitivity than conventional thermometers.