Magnetic memory signals of laser cladding Ni-based alloy on Q235 substrate are detected,and the thermal damage of laser cladding is detected by metal magnetic memory technology.The thermal damage caused by different laser cladding parameters are investigated through the magnetic memory signals.Results show that the metal magnetic memory technology can detect the thermal damage of laser cladding effectively.The thermal damage location can be predicted according to the mutational characters of average gradient curve.Quantitative assessment is made for the degree of the thermal damage based on the ratio(R) of the average gradient mutational peak of cladding region and the average gradient on all testing points.Assessment result shows that the specimen has severe thermal damage if the absolute value of the R is greater than 1,and the thermal damage degree of laser cladding will increase with the increasing of laser power,the decreasing of spot diameter,and the reducing of scanning speed.