Abstract: A welding inverter power and eddy current testing fusion system is designed according to their operation principles. The analog signal processing circuit of the exciting and receiving parts in eddy current testing is added to welding inverter power,while the digital signal processing part in the eddy current testing is shared with that in welding inverter power. The alternative square wave from the main transformer in the inverter power is filtered,then the output sine signal of the filter drives the eddy current testing probe,and the received eddy current testing signal is amplified,compared and demodulated,and then it is digitized for the following digital signal processing to realize defect testing. The experiment results show that the fusion system can add eddy current testing function to inverter power without influence on welding.