A novel bionic jellyfish robot was present to solve the problems that relatively little research about the motion performance,volume,emergency ability and so on for bionic jellyfish robot at present.Cam was used as the main part of power transmission,the bionic tentacles were used to squeeze water to generate thrust,so as to improve the motion performance of the bionic jellyfish robot.Simultaneously,the internal transmission structures relied on a single cam to drive,which reducing the volume of the vehicle and provide more space to carry additional units.The additional unit included separating the shedding structure and air bag,which enhanced the emergency response ability of the robot in the face of complex underwater situations.The relaxation and contraction time functions of the bionic jellyfish robot were established,and the theoretical value of time was obtained after inputting the corresponding design parameters.Finally,the bionic jellyfish robot prototype was made to measure its volume,and the no-load experiment and underwater experiment were conducted to verify that the designed bionic jellyfish robot had smaller volume,emergency ability and better motion performance.