The article presents the methods of determination and analysis of the continuance of harmonics in the supply current of a modern subway vehicle with an asynchronous converter power. Knowledge of the harmonic content of the supply current is a very important part of the study, allowing the vehicle to operate. In order to determine the harmonic voltages and currents, a computer model of the test vehicle and the power supply and subway substations was created. The simulation was created using the SimPowerSystem library, which is part of the Matlab program. The calculation results were compared with the measurement.