Abstract: To study the change of liquid temperature in the process of sub-millisecond pulsed discharge in water, a schlieren observation system suitable for pulsed discharge in water was constructed. The influencing factors and calibration method of the temperature diagnosis system for the process of pulsed discharge in water were proposed, and the radial distribution of the temperature field during the pulsed discharge in water was obtained. Comparative analysis with the finite element simulation shows that when the radial distance is less than 0.9 mm, the deviation of the temperature based on the schlieren diagnosis from the simulation results is less than 8%. It provides a technical basis for the study of the mechanism of pulsed discharge in water.