Abstract: According to the character about spectral control of droplet transfer in pulsed MIC welding, a pulsed MIG welding inverter power source with the IGBT double single-end positive-exited inverting circuit and its control unit are developed. The control unit takes 8098 singlechip computer to be able to quickly process spectral data as control center and the control center is connected with PWM control of welding current. Its control signal comes from a kind of are spectral signal reflecting droplet transfer.The experiments show that the power source and its control unit have the function, such as quickly collecting and processing spectral signal, good dynamic characteristic and easily on-line adjusting parameter.It has realized the control aim of 1-peak-0-base droplet transfer and becomes good base of the next test of spectrum control method of droplet transfer in pulsed MIG welding.