The goal of this master thesis was to make theoretical analysis of two-phase buck converter with coupled inductor and belonging model in Matlab Simulink. In addition graphical user interface (GUI) for optimization of coupled inductors design was made. In today’s time almost every electronic device requires a power supply device to connect to the electric grid. By modeling converter with coupled inductors, we can reduce phase ripple and with that associated losses also. Benefits of converter with coupled inductors are described in introduction. Buck converter and two-phase buck converter with coupled inductors are described in theoretical part. Waveforms of voltages and currents typical for two phase buck converter with coupled inductors along with the relevant equations are given in the second chapter. Simulation model and simulation results are presented in third chapter. In simulation results is shown how changing the parameters of simulation affects the voltage and current waveforms. In conclusion, results obtained from simulation are analyzed and compared to the results calculated from equations. Graphical user interface (GUI) for optimization of the coupled inductors design along with the code are presented in Appendix A and Appendix B.