The technical and economic indicators of power electronic devices are mostly determined by switching devices of large power.Based on engineering applications of Southern Power Grid（SPG）35 kV/?200 Mvar cascaded STATCOM，the basic structure and the operation principle of injection enhanced gate transistor（IEGT）is briefly treated，and the performance characteristics are analyzed and compared with the parameters of integrated gate commutated thyristor（IGCT）and insulated gate bipolar transistor（IGBT）.The phase-module of IEGT and the operation principle are dealt with，and the superior characteristics of phase-module are verified by experimental results.The research shows that IEGT should be the first choice of power switching devices of the high-voltage and large power STATCOM.The conclusions obtained have proved useful in actual project application of China SPG，providing a reference for high-voltage and large power STATCOM design.