Polar dielectrics are widely used as functional materials in modern microelectronics. Among them, a special place is occupied by ferroelectrics whose spontaneous polarization can be reoriented by an external constant electric field. The study of polarization switching processes accompanied by relaxation phenomena is an important problem in condensed matter physics [1-2]. In this paper, we study the relaxation of the dielectric permittivity in ferroelectric PZT films in stationary electric fields, determined from the maxima of their reversible dependences.  Unipolar thin PZT films were obtained by radio-frequency magnetron sputtering of ceramic target of PbZr0,54Ti0,46O3+10% PbO composition corresponded to the morphotropic phase boundary on ‗cold‖ platinized (Pt/TiO2/SiO2/Si) silicon substrates. The target contained additionally 10% mol of lead oxide to compensate the lead losses during high temperature annealing and crystallization of perovskite phase (Tcryst) in the temperature interval 580-650 оС. Platinum was used as the upper electrodes. The resulting capacity Pt/PZT/PZT structures were additionally annealed at a temperature exceeding the temperature of the phase transition Curie temperature.  Fig. 1 shows the relaxation dependences of the dielectric permittivity (ε) for a unipolar PZT film in stationary fields (a) determined from the maxima of reversible dependence of ε (b). As can be seen, the relaxation processes occur with three relaxation times, and more rapidly in the direction of vector of unipolarity, curve 1. The possible mechanisms accompanying the switching of polarization in polycrystalline PZT films are analyzed. In particular, it is shown that the dependences of relaxation times on Tcryst are related to the values of exceed lead oxide and its distribution in the volume of the film. Fig. 1 Relaxation of dielectric permittivity (ε), measured under application of stationary electric fields Ep (curve 1 corresponds to conditions - Еp ­­ Рself and Еp = 30 kV/cm and curve 2 – to Ep ­¯ Рself and Еp = 5 kV/cm) (a), and a determination of Еp values from the maximums of reversible dielectric permittivity dependencies δ (U) (b) of unipolar thin PZT films (Тcryst=580 оС).