Based on the characteristic of ferroelectric microstructure, a crystal cell of ferroelectric is regarded as a dipole. Analysis of the switching property of di pole in the electric filed is made. According to the statistic principle, differ ent distribution functions are used to fit the probability of dipole switching. A model based on hysteresis loop is developed. Experimental data on PZT show go od agreement with the model for various loops, and the model is easily linked to simulative software of circuit for either memory or analog design application.