According to the recommendation of CIPM, the Quantum Hall Resistance (QHR) standard has been used worldwide since January 1~(st) of 1990 to replace the traditional resistor standard, which had been maintained for several decades. After the effort of more than ten years a Quantum Hall Resistance standard was established at NIM in 2003. The QHR samples were produced independently in China. At the same time, the necessary Cryogenic Current Comparator (CCC) with high precision for disseminating the QHR values t...