Abstract: Crack-free laser-cladding layers with high hardness were obtained by using self-made Fe-based alloy powders for laser cladding without preheating and tempering.This paper revealed the mechanism of strengthening and toughening of the developed Febased alloy.The mixed martensite with medium carbon content contributes high hardness and high strength, as well as somewhat toughness; the retained austenite, which is distributed along grain boundaries, contributes excellent plasticity and toughness.The retained austenite can absorb and reduce the stress of the layers, and decrease the cracking susceptibility while it will not obviously decrease the hardness and strength of the cladding layers.