The phonon vibration frequencies of PbZr x Ti 1- x O 3( x =0 25～0 40)at Г point in the Brillioun zone were calculated by using the rigid ion model in the frame of the virtual crystal approximation. The results show that the transverse optical phonon frequencies of PbZr xTi 1-x O 3 shift toward the lower frequency with increasing composition x of Zr, which is in accordance with the data of Raman experiments.