Abstract: In order to achieve effective prediction of the equivalent parameters of dielectric barrier discharge piecewise model, discharge region is introduced as an intermediate variable in the proposed method. In this study, taking parallel ceramic rods as the reactor, the corresponding relationships between the equivalent capacitances of the reactor and the discharge region are obtained by Maxwell finite element simulation under constant voltage electrostatic field. With the help of electric field distribution, the estimation theories of how the critical parameters change over the gradual expansion process of the discharge region are explained, including the air gap first breakdown voltage, the peak value of the applied voltage and the air gap discharge maintaining voltage. Afterwards, the discharge power under various operating conditions can be calculated by Lissajous's figure method. Thus the quantitative relationship between the discharge region and each equivalent parameter is established, and the prediction is realized. An experiment for verification was performed with air gap distances of 1 mm, 3 mm, and 4 mm. It is shown that the predicted and the experimental curves of discharge maintaining voltage have some difference in the local variation trend, while the discharge power and the applied voltage peak prediction results are in good agreement with the measured ones.