Abstract: Quite a few disadvantages can be found when using an AXT - 2 X 205 type self - propelled, crawler - mounted two - arc welder: severe engine wear, high fuel consumption, quick wear of rotating connection, unstable rotary speed of diesel engine, etc? Through analysis on the performances of the welder and selection of operating points of diesel engine, it is concluded that the only way to slow down engine revolution rate is to raise the power factor of the generator of arc welder. As seen from generator7 s external characteristic curve, the power factor can be raised by improving the 3rd welding dynamic characterstics, to improve arc elasticity and reduce the deviant of welding current. Using the control instrument, a newly produced device for improving welding dynamic characterist.cs by means of electronics, can slow down the operating point of engine from 1500r/min at one hours (high speed) to 1250r/min at ten hour (lower speed). Also it has the function of current remote control and preventing electrode from bonding. The efficiency is raised from 61 % to 74%, and fuel consumption is reduced.