Theoretical and experimental results of the intensity profile modification of a Gaussian laser beam by 2-D ultrasonic standing waves are reported. The results indicate that the Gaussian intensity profile of a focused laser beam can be modified by a 2-D ultrasonic standing wave when the spot size of the Gaussian laser beam on the input face of the acoustic cell is small than the ultrasonic wavelength. The intensity of a focused laser beam can be made nearly flat in the central region if the acoustic pressure properly controlled. The flatness and the flat region can be changed continuously by varying the acoustic pressure.