A novel fluid power actuator called Flat Ring Tube (FRT) is introduced in this paper. The mechanism of FRT is so simple that it only needs a urethane flat tube and water pressure power source. No valves or switches are required. Applying constant water pressure results in periodic oscillation of the tube. The frequency is proportional to the flow rate of water and inversely proportional to the tube length. By contacting the tube with a passively supported shaft, it rotates due to the periodic tube oscillation. This principle can also generate the linear driving force, when FRT is mounted so as to kick the ground. Such kind of performance can be also expected to stimulate the blood flow rate, when FRT touches on the skin of the human body appropriately. The experimental results showed us the developed wearable massage device could effectively improve both the circulation of the blood flow and the density of oxygen in blood, which resulted in let the people feel more comfortable than conventional massage devices.