The dynamic behavior of two collinear anti-plane shear cracks in a piezoelectriclayer bonded to two half spaces subjected to the harmonic waves is investigated by a newmethod. The cracks are parallel to the interfaces in the mid-plane of the piezoelectric layer.By using the Fourier transform, the problem can be solved with two pairs of triple integralequations. These equations are solved by using Schmidts method. This process is quitedifferent from that adopted previously. Numerical examples are provided to show the effectof the geometry of cracks, the frequency of the incident wave, the thickness of thepiezoelectric layer and the constants of the materials upon the dynamic stress intensity factorof cracks.