In the operation of large current switch cabinet, the thermal phenomena caused by eddy current losses is serious. In order to study the eddy current loss in the switch cabinet, a calculation method of eddy current loss is derived in this paper. Then a simplified switch cabinet model for the magnetic field calculation is established by SolidWorks. In addition, the losses of busbar in AC and DC load conditions are calculated through the finite element simulation software. It is found that the skin effect and proximity effect have influences on the busbar heating. Then the eddy current field of the entire switch cabinet is simulated and the eddy current loss for entire cabinet is obtained. Finally, several optimized suggestions are put forward according to the calculation results. It is found that eddy current loss in switch cabinet is large, which reaches 3 831.66 W. Therefore, the eddy current loss cannot be ignored in the calculation of temperature rise in the switch cabinet.