Abstract: Based on the characteristics of redundant and multidegree of freedom of bionic snake, the mechanical mechanism of PR structure snakelike robot is proposed. The main feature of this mechanism is its modular joint. Each joint has three degrees of freedom, spring parts are used in joint structure, and each joint has two motors. When the motor has no force, the spring returns to the initial position through the pre-tightening force. No electric and program control are needed, the operation process is greatly simplified. The movement of the robot is more fitting to the surface of external environment, increasing its stability during task execution. Breakthrough functional postures such as axial expansion, back and abdomen bending are achieved.