Abstract: The circumferential weld quality of the enormous corner joints between the heat exchange tube and plate in the medium-sized or large scale heat exchangers(condensers) is the key to ensure the manufacturing quality of heat exchangers,which need full position automatic precise welding technology.A full digitalized and low cost tube-plate welding power supply based on ARM(advanced RISC machines) was proposed.The full bridge inverter topology was adopted in the main circuit.The LM3S8971 with 32 bits Cortex-M3 kernel was used as the core of the process control of welding power source,and the full digitalization control of the welding process was realized.The digital control panel of the welding power source based on ARM CPLD(complex programmable logic device) was designed to make man-machine interactions really come true.The function test and experimental research on the welding power supply demonstrated the excellent performance of the system and fulfilled the demand of the full position automatic tube-plate welding process of heat exchanger.