With the development of rotorcraft and the increasing complexity of the environment in many missions, single sensor has shown obvious deficiencies. Therefore, better autonomous navigation is needed to complete all kinds of urgent and dangerous tasks. Starting from the basic concepts of vision and inertia, this paper comprehensively analyzes the advantages of this kind of combination. Then, the basic situation of rotorcraft is introduced, and the key technologies of vision/inertial navigation based on rotorcraft are analyzed, including front-end for vision, initialization and fusion methods. Particularly, more outstanding algorithms in recent years are introduced, which help us understand their advantages and disadvantages better. Finally, according to the existing literature, problems that need to be further studied of vision/inertial integrated navigation for rotorcraft are summarized and analyzed.