Nowadays, as the size of Very large scale integration (VLSI) is getting smaller, thermal effects are playing an important role in the system since the high temperature can affect the performance of the system. There is a various of method in determining the thermal profile of VLSI system. The focus of this study is to implement Crank-Nicolson (CN) method in discretization of the heat equation to obtain the linear system. The linear system will be solved by using iterative methods, Gauss Seidel (GS) and the proposed successive over relaxation (SOR) method. Then, a comparison of the efficiency between these two methods will be analysed based on iteration counts, computer proses time and the maximum temperature. The numerical results show that SOR is more efficient compared to GS. Therefore, the results for this study may be beneficial for the future research in solving numerical iterative method. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.