RF superconducting cavities can work at CW mode or long pulse mode with high accelerating gradient. RF superconducting technology is widely used in particle accelerators. A lot of front scientific facilities are set up based on RF superconducting accelerators from low beta to high beta. RF superconductivity has become a most important technology in FEL and ERL. In the recent 30 years, the technology has made rapid progresses. The accelerating gradient can be over 40 MV/m by special treatments. High accelerating gradient is the front research in the field of RF superconductivity. EP + bake can provide an important method to increase the accelerating gradient. The accelerating gradient can increase by 3~4 MV/m after EP + bake treatment and the Q-drop is also improved. Recent developed dry tr