Electronic Current Transformer (ECT) is one of the key equipments of the Smart Gird, but because of its operating principle, many optical devices and electron devices are used, and it is easily influenced by temperature variation. Now, the test methods and requirements of the ECT’ temperature cycle test that proposed by the IEC-standards, the Chinese Government standards and the Performance Test Schemes of State Gird are so simple that they cannot meet the demands of complex environment in the transformer substations. We have done some analysis to improve the test methods and requirements, and we put forward the test methods and requirements to measure the ECT’s temperature characteristic in real-time in the whole temperature range. We conduct some verification tests on the selected sample machine of the ET, and this paper suggests that it is more useful to evaluate the ECT’ temperature characteristic.