Abstract: The dynamic distribution of optical radiation intensity along the central axis of pulsed-current micro-plasma arc was investigated under different pulse parameters. The results show that the distribution curve of radiation intensity along the arc axis had double peaks. The pulse parameters, including base current, peak current, duty ratio, frequency, affected the distribution of radiation intensity along the arc central axis during pulsed-current micro plasma arc welding. And the effect presented different degrees of "thermal inertia" with the change of pulse parameters.