Abstract: A cladding of Cusi3 was deposited on the suface of 30CrMnSi steel by the method of cold metal tromsfor(CMT).The microstructure characteristics and compositions were investigated by back scattered electrons, energy dispersive X-ray spectrometry and X-ray diffractioin.The results show that the metallurgical bond of cladding and base metal is carried out with CMT technology.When wire feeding speed(v_s)is 5.0 m min and welding speed is 17 mm s, the rate of dilution is extremely low.Fe₃Si, α-Fe, ε-Cu formed in the interface.The interface microstructures are Fe3 Si α-Fe +ε -Cu α-Fe when vs is slow.The feeding speed have a significant influence on the cladding layer.With the increase of v_s, the interface microstructure change to Fe₃Si +α-Fe +ε-Cu α-Fe +ε- Cu.When v_s is high, the structure of α-Fe +ε-Cu is obtained. With the increase of v_s, Fe-rich phase in the cladding increased dramatically, gathered and grew from disperse nodular phase to stellated α-Fe solid solution.