Abstract: In order to optimize twin-wire three-arc surfacing parameters and predict surfacing dilution rate and welding current, mathematical models between surfacing parameters such as current between twin-wire (M-arc current) and main arc voltage, and dilution rate and welding current were established based on response surface method. Design-Expert software was used to carry out variance analysis, model significance test and model signal-noise analysis on response of dilution rate and welding current. Influence of surfacing parameters on dilution rate and welding current was studied, and surfacing process was optimized and verified. The results showed that M-arc current had a significant effect on welding current and dilution rate. Increasing M-arc current, welding current decreased, melting amount of base material became smaller, and dilution rate became smaller. Reducing excessive entry of melted base material into surfacing layer and ensuring effective components of metal powder cored wire was beneficial to control of microstructure and wear resistance of surfacing alloy material. The optimal surfacing parameters were obtained by optimizing the design. Main arc voltage was 35 V, M-arc current was 260 A, wire feeding speed was 10 m/min, frequency was 70 Hz, and duty cycle was 50%.