Abstract: A study of SCR arc welding power source comprising a microcomputer to implement digital control for obtaining multiple static volt-ampere characteristics was made.It is found that the optimum constant current static characteristic can be obtained by using the feed-forward plus proportional-integral control algorithm,and that the constant current with arc force control characteristic,dropping characteristic with different slopes,and constant power output characteristic can be achieved by utilizing the algo-rithms and flowchart described in this paper.Furthermore,the interface between use rand machine is available for the setting of the characteristics and paramters required.