Abstract: The mechanisms of two kinds of magnetic field mainly distributed around power source and cables are analyzed,and their accuracy is verified through measurements.It's found that several modulation effects on current from rectifier to inverter module in the power source result in stacking effect of magnetic field among power-frequency magnetic field and magnetic fields generated by the rectifier and inverter module.Furthermore,the magnetic field frequency around the cables strongly depends on the frequency of IGBT;low-frequency and time-varying magnetic field strength increases as the current ripple increase,but varies inversely as distance approximately.Extra electromagnetic radiation to operator results from closing to and bending the cables,therefore,it's great significant to further understand and descript the electromagnetic radiation under welding environment to standardize the welding criteria and also to reduce magnetic filed radiation exposure as far as possible.