This paper investigates new pumping phenomena induced by surface waves in a microchannel. Acoustic streaming is known as fluid motion due to high intensity sound. This phenomenon usually occurs near an oscillating surface of a body in a sound field. In this study, a new acoustic pumping mechanism, different from surface acoustic streaming phenomenon, is found. According to current parameters, the new pumping mechanism can generate net flow rate about 10 times higher than the surface acoustic streaming pump. We investigate this new pumping mechanism numerically. The new pumping mechanism is further identified as results of pressure wave resonant behaviors due to finite length of microchannel. The length scale related to pressure wave resonant behaviors is found to be δL=L/π, where L is channel length. The effects of parameters including frequencies, channel heights, channel lengths and wave lengths on the velocity profile and net flow rate are also investigated..