Abstract: The thermocouple is the most widely used temperature sensor in the vacuum thermal tests of spacecraft. Its manufacturing process directly affects the product quality and reliability. Taking the manufacturing process of Cu-CuNi fine thermocouple as an example, this paper proposes and has realized a new method to complete the welding of thermocouple by the high-pressure discharge technique under the protection of inert gas. This method is characterized by easier operation and higher rate of acceptability, which greatly improves the efficiency of thermocouple's manufacturing. Besides, the problem of introducing another material during the manufacturing process is avoided.