Abstract: CO₂ short circuit arc weld process,widely applied to manufacture industry,should be matched with such a power source system with good dynamic characteristic.Based on the careful analysis to the process dynamic characteristic and output characteristic according to the electric circuit theory and welding property of short circuiting transfer process,this paper breaks through the traditional idea,a confused and independent idea in relation to output characteristic control and dynamic characteristic control.Then a new viewpoint is put forward in which the CO₂ short circuiting arc welding process,a close relation occurs between output characteristic and dynamic characteristic.For one thing,the dynamic process can not be explained on the basis of the dynamic characteristic control.For another thing,the dynamic characteristic is related to the output characteristic and restricted by that.Furthermore,an idea about the fastest responding and controllable dynamic characteristic of a welding power source has been developed.Great theoretical meaning is attached to the analysis with clear math language to the relationship between the above two kinds of characteristics.