A new type of pneumatic flexible fivefingered robot hand imitating the human hand based on bionic principles was designed. The structures of the fingers adopted the modular design concept, and each finger was composed by single bending joints and muti-directional bending joints in series. The grasp experiments were done on the pneumatic control platform of the robot hand. And the experiments show that the robot hand has good flexibility to adapt the shape of the object, and it can grasp objects of various shapes, such as sphere, cylinder and box and so on.