Abstract: To reduce the error between the calculated value of metal absorptivity by Fresnl formula and the measured value, the factors affecting metal absorptivity in the laser heat treatment were analyzed, and the mathematical model of metal absorptivity was improved by simulation. The model was used to calculate the absorptivity of aluminium, copper, platinum, iron and 3Cr13 stainless steel. The calculation result agrees with the value measured with lumped parameter method, which proved the validity of the improved laser absorptivity formula.