Abstract: In order to obtain the optimal cladding process parameters of extreme high speed laser cladding of Fe-based self-fusible alloy powder on 40 Cr steel matrix of high pressure piston pump, central composite design in response surface methodology（RSM） was used to design extreme high speed cladding test. The effects of laser power, powder feeding rate and workpiece rotating linear speed on the aspect ratio, dilution rate and microhardness of the extreme high speed laser cladding layer were discussed. The mathematical model of response surface method was established and the technological parameters of extreme high speed laser cladding were optimized. The optimal cladding process parameters optimized by RSM were tested and verified, and the key response targets of the cladding layer were improved as expected. The results show that RSM is an effective method for multi-response target optimization of extreme high speed laser cladding process parameters. The research lays a technological foundation for the surface modification or repair of the high-pressure plunger surface and the preparation of high-quality cladding layer.