The invention relates to a preparing method of PZT-based piezoelectric ceramics. The problems that PZT ceramics are low in piezoelectric constant, poor in temperature stability and short in service life can be effectively solved. The preparing method includes the steps that PZT powder and MnO2 powder are mixed, water is added, ball-milling is carried out to obtain slurry, the slurry is dried, a binding agent is added to form a blank, the blank is formed in a pressed mode, piezoelectric ceramics are obtained through binder removal and sintering, polished and coated with silver paste to form silver electrodes on two surfaces, then the piezoelectric ceramics are put into silicone oil, electric field polarization is carried out for 5-60 min to obtain the PZT-based piezoelectric ceramics. The PZT-based piezoelectric ceramics is rich in raw material, scientific in formula, simple in preparation method and excellent in product performance, piezoelectric parameters are increased, the service life is long, and the piezoelectric ceramics are innovation in the field of piezoelectric ceramic materials.