This paper described the structure of a flexible miniature robotic system which can move in humancavities,and then analyzed the characteristics of the robotic system in detail.The mobile mechanism ofthe miniature robotic system is soft;it makes inchworm-like movement driven by a 3-DOF pneumatic rub-bet actuator and holds its positions by air chambers.The driving characteristic models in axial and bend-ing directions of the actuator were set up and the kinemics equations of the robotic system were set up.Experiments had been done through an electro-pressure control system,by which the pneumatic roboticsystem can be controlled with high accuracy.It is suitable for moving in human cavities for medical in-spection. This paper describes the structure of a flexible miniature robotic system which can move in human cavities, and then analyzed the characteristics of the robotic system in detail. The mobile mechanism of the miniature robotic system is soft; it makes inchworm-like movement driven by a 3- DOF pneumatic rub-bet actuator and holds its positions by air chambers. The driving characteristic models in axial and bend-ing directions of the actuator were set up and the kinemics equations of the robotic system were set up. Experiments have been done through an electro -pressure control system, by which the pneumatic roboticsystem can be controlled with high accuracy. It is suitable for moving in human cavities for medical in-spection.