Combustion experiments were conducted to research the high-frequency combustion instability of the liquid-propellant rocket engine. Kanda conceived that off-design combustion would be cause of the high-frequency instability. The experimental model was designed to simulate the off-design combustion space created by the propellant jet and the injector wall surface. Propellant were 2-propanol and gaseous oxygen. In the experiment, there was a pressure increase of 1.5 to 3.3 times as high as the ambient pressure. Pressure increase time was located from 0.03 to 1.84 milliseconds The experimental results were similar to the pressure changes reported under the actual high-frequency combustion.