Abstract：Due to the harmonic and reactive power caused by electric locomotive,a simplicified device,composed of a master board and a single power unit,is designed.The architecture of master board is DSP FPGA.The controller of power unit using a CPLD,instead of lots of logic gate chips.It mainly describes circuit design,selection of electronic component and its parameter settings.Experiment on this device,the result shows that the device has a good compensation characteristic and a certain value of engineering applications.