In recent decades, a lot of research has been done on snake-like robots. There has been a new revolution in theory and implementation of snake-like robots. It enlarges the field of robotic application. A literature survey of researches on snakelike robots theory is provided biomechanical studies of biological snakes, kinematics and dynamics modeling, control system analysis. The research theory results are elaborated systemically. In particular, control system is introduced ulteriorly, which are control based on morphology, kinematics and dynamics, CPG. Then classifications of typical snake-like robots are presented according to the differences of structures and movement types. Representative snake-like robot bodies are described targetedly in detail. Finally, the development of snake-like robots is predicted. The overview shows that the majority of literature on snake-like robots so far has focused on experiment instead of the real, but there is a growing trend towards locomotion in realistic environments that are more challenging in future.Index Terms -snake-like robot, biomechanics, control system, body design.