The metal surface of laser heat treatment is generally processed by mechanical processing, with small surface roughness and high reflectivity to laser. Before laser heat treatment, the quenched surface should be pre treated to improve its absorbance. After oil removal, rust removal, cleaning, and drying of the treated surface, a light absorbing coating (blackening) is pre installed on the surface. The methods include phosphating, spraying (brushing) paint, improving surface roughness, oxidation, coating, etc; The coating should be thin, uniform in thickness, with a high laser absorption rate (over 90%), good thermal conductivity, good adhesion to metal, and not decompose or evaporate at a certain temperature. It is easy to clean and remove after quenching or can be used without removal.