This study focuses on the current-carrying temperature rise issue of the key electrical connection points in the high-voltage connection system of new energy vehicles. A test bench was set up, including a DC power supply, a constant temperature chamber, and data acquisition equipment. Two working conditions of 380 V high voltage and 15 V low voltage were selected to conduct comparative tests on four groups of the same current conditions of the main circuit and the electric drive circuit. The results show that the temperature rise difference between high and low voltages in each group is only from 0.02 to 0.69 K, which is less than the sampling error of 1 K of the equipment; the maximum temperature rise of the system reaches 48.87 K, and the peak temperature is 112.87 ℃ , all meeting the national standards and temperature limit requirements of components. The study indicates that under the same current conditions, the influence of the added voltage level on the current-carrying temperature rise of the high-voltage connection system can be ignored.