Abstract: In tokamak plasmas, the confinement performance can be significantly improved in high confinement regime. Investigation on the plasma instabilities in this regime is important for the confinement control and steady state operation of tokamak. This paper mainly introduces the researches on the high confinement mode and underlying edge plasma instabilities. It emphasizes on the studies on high confinement mode transition, features of edge-localized mode and its control, pedestal instabilities and pedestal saturation mechanism. The study suggests that pedestal dynamics and edge-localized mode might be actively controlled by the pedestal turbulence, resulting in the steady state operation both with high confinement performance and low heat loads on plasma facing components.