Micro nano scale surface structure has many special properties and applications in surface engineering.In order to study the mechanism of femtosecond laser preparation of stainless steel surface micro nano structure,the process of femtosecond laser ablation of 304 stainless steel is based on the classical dual temperature model theory.Numerical simulation calculations were carried out.The evolution law of the electron and lattice system temperature at different laser energy densities and different ablation depths is obtained by calculation,and the ablation threshold under the action of a femtosecond laser single pulse is determined.Through the numerical simulation,it is obtained that the femtosecond laser ablation of stainless steel only occurs on the surface of the material,and has little effect on the internal material.Finally,the micro nano structure on the surface of the stainless steel is made by a femtosecond laser micro nano processing system.The polygonal micro hole structure maintains high quality edge morphology,and a periodic structure appears on the inner wall of the hole.