In this paper, the dynamic behavior of two collinear anti-plane shear cracks in a piezoelectric layer bonded to dissimilar half spaces was investigated for the impermeable crack face conditions. The cracks are vertical to the interfaces of the piezoelectric layer. By means of the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved by use of the Schmidt method. This process is quite different from that adopted in previously. Numerical examples are provided to show the effect of the geometry of the cracks, the piezoelectric constants of the material and the frequency of the incident wave upon the dynamic stress intensity factor of the cracks.