Aiming at the problem of poor grasping stability of soft manipulator,a variable structure pneumatic soft three-finger manipulator consisted of a switching mechanism and soft fingers was designed.The manipulator could realize four grasping modes,and the working space of the soft finger could be changed by transforming the structure of the mechanism,making it in the best grasping position.A mathematical model of finger single chamber bending was established to obtain the relationship between inflation pressure and bending angle.The influence of various parameters on the bending angle was analyzed by finite element method,and the structure of the chamber was optimized.The good performance of soft finger was verified by inflatable bending test.The relationship between the input pressure and the output force was obtained by the soft finger output force test.The prototype was made and eight kinds of objects were grasped by experiments.The results show that the manipulator is stable and can realize the non-destructive grasp of various irregular objects and objects with different hardness and softness in the range of 0~320 g.