A Study about the Oscillation of the Water Pistons of the Fluidyne Heat Machine ( A Study about the Oscillation of the Water Pistons of the Fluidyne Heat Machine (II) For the teaching materials of the school science Nobukazu KIRIYAMA Ph. D tract was carried out by changing the length of the two pistons' connecter cr Water Stirling Engine (Fluidyne Heat Machine). As a result, the relations of the phase difference led by preservation of the water and a simple oscillation model was able to explain experimental value enough. And the fact that frequency in the most suitable length of resonance pipe is smaller than a prediction, and the amplitude of the power piston has a bigger than a prediction is explained by the model to change the flow of the water by viscous 1:c:jstance. In addition, by simultaneous measurement of surface oscillation of the water pistons and the pressure, it was proved that pv diagram of the water stifling engine is near to an ideal stilling cycle. Finally, a figure of device of the hydraulic power generation by working to \water using the water stilling engine was showed as the energy teaching materials. Keywords: Fluidyne,oscillation of water piston,hydraulic power generation 16