Abstract: With the continuous development of integrated circuit and its packaging technology, the power density and current density in its power transmission network are increasing day by day, so it is necessary to consider the coupling effect of Joule heat effect and material conductivity property in the design of integrated circuit. In this paper, a numerical method of electro-thermal coupling based on finite element method is implemented to calculate the voltage drop of IC's PDN underconsidering the interaction between electricity and heat.However, the inhomogeneous distribution of conductivity and other physical parameters caused by some boundary conditions is found in the calculation of electro-thermal coupling.To solve this problem, the idea of inhomogeneous parameters and the vectorized parameters updating method are proposed. Considering the iterative coupling relationship between inhomogeneous physical quantities, the inhomogeneous temperature distribution and potential distribution in power transmission are calculated. Compared with other two commercial software, the algorithm shows higher time efficiency, which provides a basic reference for the design of integrated circuits.