This paper introduces briefly technology and application of Automatic Testing System of 0.4kV Current Transformer and some relevant issues of the system are discussed. Some ideas of trace to the source are provided for the current transformer test of magnetic saturation error and secondary winding inter-turn insulation. The upper volume is disproportionate to the secondary load and suggestion is proposed that The upper volume is set to 1VA. Secondary load is required to strengthen measure. The repeatability and multiple output consistency of this system are measured and find that the main reason is the existence of contact resistance of relays and poor contact on two terminals of current transformer. Measurement process control is acted on the repeatability and stability of the system according to the Shewhart control chart. Finally, it discusses the lab control of temperature and relative humidity and gives the advice.