The paper introduces a principle and application of power supply that gets energy from high tension line for electronic current transformers (ECT). Some problems of designing the new type of active ECT with self-excitation power supply and the relevant techniques and methods are fully studied. The ECT with self-excitation power supply has successfully created and put into practical. The wake-up current of the new ECT is only 0.588 A and Wake-up time is less than 20 ms.The original restricting electrical current "funnel structure"（a special restricting current component）is used to have solved key technology problems of impacting system by saturation large current. With some other special technical measures，self-excitation power supply can make sampling and transmitting circuit work in the purifying power and ensure measurement accuracy. The whole technology of creating the ECT with self-excitation power supply not only has simplified the structure of the ECT and also has achieved a major breakthrough in optical isolation ECT technology of china，that greatly lift the integrated automation level of power system. The new type of ECT has been approbated durable products and has entered the electric power market.