Helicopters possess unique advantages such as vertical takeoff and landing, hovering, and low altitude maneuvering flight, playing crucial roles in military and civil aviation. However, issues such as low speed, high fuel consumption, limited range, and high noise levels, have become constraints on expanding the application market of helicopters in both military and civil sectors. Variable rotor speed technology offers a solution by dynamically adjusting rotor speed according to flight conditions, effectively mitigating these shortcomings and improving helicopter performance. Consequently, it has emerged as an important research area in helicopter technology. Currently, variable rotor speed technology faces numerous challenges concerning its impact on helicopter performance, optimization and control, controls derived from variable rotor speed technology, and implementation. This paper provides a summary of research findings on variable rotor speed technology, focusing on three key aspects: the impact analysis of variable rotor speed on helicopter performance, optimization and control methods, and the realization of variable rotor speed technology. The aim is to provide a valuable insights into the development of variable rotor speed technology of high-performance helicopter.