Abstract: On the basis of cognition of the potential significance of welding arc spectrum dynamic characteristics and with the destination to find out new sensoring method of metal transfer,this paper provided the parasynchronous principle and in turn verified the relationship between the pulses in the waveform of arc spectrum signals and metal droplet transfer with para high speed photography apparatus.The testing result shows that the pulses in spectrum waveform were correspondingly brought up by droplet transfer,the pulses could be applied in process and quality real-time control where metal transfer must be exactly detected.Meanwhile,the reason and theoretical explanation of pulse appearance were given.