Physical properties of polycrystalline ferroelectrics including the contributions of the fixed dipolar defects and the average grain size in the Potts-Ising model are simulated by using the Monte Carlo method. Domain patte, hysteresis loop and switching current of the polarization reversal process are obtained. Two processes are considered in our simulation. In the first one, the grain texture of ferroelectric ceramics are produced from the Potts model, and then the/sing model is implemented in the obtained polycrystalline texture to produce the domain patte, hysteresis loop and switching current. It is concluded that the defect has the ability to decrease the remnant polarization Pr as well as the coercive field Ec. The back switching is obviously observed after the electric fieId is off, and it shows some variation after introducing the fixed dipolar defect. Meanwhile, the spike of the switching current is found to lower with the increasing defect concentration and the decreasing average grain size.