The dynamic nature of phase synchronization between chaotic outputs and inj
ected periodic signals is investigated. We find that the collapse of strobo
scopic section from global distribution to local one and the loss of homoge
neity of stroboscopic sections in chaotic attractors for different phases a
re the key features of this kind of phase synchronization, meanwhile the ov
erall structure of chaotic attractor is not affected apparently by the phas
e synchronization.