[en] The author presents the thermocouple penetration assemblies of 10MW high temperature gas cooled reactor(HTR-10). The thermocouple penetration assemblies, which consist of penetration pipe, assemblies of sheath thermocouple and protective pipe for welding, are used to measure the temperature of components in the reactor. The laser welding technology is used to weld the transition pipe that is designed specially to the sheath thermocouple, and the argon arc weld(TIG) is used for welding the transitional pipe to the penetration pipe. So the difficult problem of sealing under high pressure and high temperature in helium gas environment is solved. By using the long sheath thermocouples, which pass through the containment and are sealed by the swage lock, the traditional commutator for temperature measure signal is avoided. By analysing and calculating with ANSYS program, the structure designs are proved to meet the case for the requirements of stress and earthquake-resistant. For authors' thermocouple penetration assemblies, the leakage of helium gas is less than 1 x 10^-7Pa·m³/s. Passing serial strict test, the thermocouple penetration assemblies have already been fixed in the reactor by now