In this paper, analysis of coaxial cable is used to reveal how an electromagnetic wave propagates in an electrical conductor, and a new modeling language, MODELICA is introduced. Some transmission line properties, such as propagation delay, reflection coefficient, attenuation, are all verified by comparing the results from MATLAB and MODELICA. The models we simulated are different types of coaxial cables, including lossless cables and lossy cables. It can be shown that MODELICA, a very powerful and convenient tool, can process complex physical systems.