Abstract: Power converters of inverter welding power supply with full-bridge or half-bridge topologies can be equivalent to Buck converter. Based on discrete modeling of Buck converter, the deadbeat control law, which could be applied to the closed-loop control of inverter welding power supply, is established by using direct time-domain derivation. The control algorithm takes a full consideration to the influence of the deviation between model parameters and actual parameters. The stability and control effect of designed deadbeat control are affected by the variation of output filter inductance. The stability condition is that the maximum inductance value used in the model is no more than 1.67 times of the actual inductance value. The simulation results show that, the system is deadbeat control only when the model inductance value equals the actual inductance value; there is no steady-state error, output ripple and overshoot by designed deadbeat control in the matching situation of model parameters and actual load parameters.