Abstract: An audio amplifier for portable devices is provided, which includes a hollow or a solid shell body and an inner container receiving in the shell body, a large opening for sound transmission is defined on the front of the shell body, and a groove is disposed on the top of the shell body, a sound absorbing aperture is defined at the bottom of the groove, the inner container comprises a curve-shaped pipeline which extends inwards from the sound absorbing aperture to the shell body until arriving the large opening for sound transmission, and the width of the curve-shaped pipeline is increased gradually as the curve-shaped pipeline extends inwards.