Abstract: ZRJ-03, a Intelligent Calibrating Unit for Thermal Meters's is the product developed from the knowledge on computer, microelectronics, and automation. Based on the installation and adjustment and the analysis on error sources and comprehensive uncertainty, it is concluded that the general uncertainty of the standard unit for Class Ⅱ thermocouple is ±1.2 ℃, and that for Class Ⅱ platinum resistance thermometer is ±0.11 ℃. Proving and comparison tests are made respectively for two sets of chromel-nickel-silicori thermal couples for Class Ⅱ service and two sets of platinum resistance thermometers for Class B service. The proving results between them show a certain conformity, with the differences less than times the general uncertainty of the standard unit.