In electrical systems, power cables are often arranged vertically. Some past researches mentioned that treating conductors arranged vertically to a ground (e.g. transmission tower, wind turbine and so on) by EMTP was difficult. Recently, FDTD (Finite Different Time Domain) method has been applied to the surge simulation regarding the vertical conductor, and the method has high accuracy for the surge simulation. VSTL rev. (Virtual Surge Test Lab. rev.) is a surge analysis program based on FDTD method. However, in FDTD method, the more complex the analysis model becomes, the longer the calculation time is needed. Therefore, we believe that it is necessary to propose an appropriate modelling of EMTP to the power cable analysis. In our research, the proposal of the EMTP model of a vertical co-axial cable is aimed. In this paper, VSTL rev. and EMTP models regarding the simulation of the co-axial cable, and the comparison of these simulation results are discussed.