The flame stabilization method using thermo-acoustic oscillation was demonstrated and the effectiveness of the sound for the flame stabilization was validated by investigation of the lift-off height change in a standing acoustic field which is a simple acoustic system. The insight of stabilization mechanism, focused on the variation of temperature, flow fields and reaction rate, was validated by CFD tool. To form the stabilized lifted diffusion flame and deal with as two dimensionally, 2D flame which formed in the mixing layer of the air and the fuel was employed for the analyzed flame. Thermo-acoustic oscillation was generated by forming flames in two stainless resonance tubes which are placed face to face. This oscillation was applied to the flame which is held by a cylindrical flame holder at the center of stainless resonance tube's open ends. Standing acoustic field was generated by two loud speakers which are driven at the resonance frequency in a stainless resonance tube. As a result, the flame was stabilized by thermo-acoustic oscillation without the flame holder. It was found that the flame lift-off height decreased with sound both from the experimental result and the CFD result. Flow speed normal to the sound propagation direction and temperature oscillated with sound.