The aim of this study is to calculate the electrical field (EF) of some types of high voltage insulators by using numerical methods. There are different methods, which are used to do this, finite element is the most important one. It is possible to find EF in 2D or 3D systems by using Matlab/pdetool, which distinguishes with big capabilities in calculation and view the results, additionally, it is available, cheap and can save time and money for doing this important calculations in high voltage applications .