A novel integral equation method for analysis of the power integrities in power distribution networks is presented in this paper. The electromagnetic field inside the power distribution network is expressed in the modal field distribution. The modal field is then expressed by using the Dyadic Green's functions. Integral equations are created for these modes. During the discritization of the integral equations, network ports are defined between the power-ground planes. Their equivalent networks are extracted through the moments method solution of the integral equations. This circuit model can be used for the signal and power integrities analysis. Through numerical examples, the accuracy and efficiency of the proposed method is verified.