The structure of two compositions of La-doped Pb(Zr,Sn,Ti)O-3 ceramic near the FE-AFE phase boundary were analyzed with normal and synchrotron radiation XRD, their remanent polarization, dielectric loss and dielectric constant under hydrostatic pressure were measured. A ferroelectric-antiferroelectric phase transition would take place between 1500 similar to 2800 atmosphere pressure for the ceramics.