This paper first briefly reviews the types of the dynamic instability of helicopter rotor/airframe, including the isolated blade dynamic instabilities such as the rotor flap-pitch coupling, pitch-lag instability, the coupled flap-lag aeroelastic instability, the flap-lag-pitch coupled instability, and the coupled rotor/airframe instabilities, such as the ground resonance and the air resonance. The related studies are reviewed from 3 aspects, the aerodynamic and structural numerical models with high precisions, the numerical methods of dynamic stability, and the model testing. The major fields of the analytical technology for dynamic stability of helicopter rotor/airframe are discussed, including the rotor aeroelastic stability analysis using the coupled computational fluid dynamics/computational structural dynamics, the dynamic stability analysis of composite rotor with consideration of material uncertainty, the dynamic stability analysis of coupled rotor/airframe with lag damper, and helicopters with advanced configurations. In the end, the future development of dynamic stability of helicopter rotor/airframe is commented.