We do some research on E-H mode transition of inductively coupled plasma (ICP) in the interlayer chamber, using the microwave phase and plasma spectrum diagnotic technique. The mode transition between E and H mode is a sudden changes phenomenon. The input power of the transition varies as the pressure changes in the chamber. The transition power from H to E is less than from E to H, so the hysteresis in power hence is established. The change of the relative spectral intensity is basically the same the variation of the electron density with input power. We obtain a stable plasma source, with an electron density ranging from 3.85× 1011 cm-3 to 4.68× 1011 cm-3, an outer surface area of 0.3 m2, and a thickness of 2 cm.