From the theory of phase transformation and thermal elastoplastic, and based on experimental data of laser quenching, a non linear coupling heat conduction equation considering phase transformation, temperature field and variable physical properties can be estabilished. A model of the relationship between the phase transformation producers and the material properties is put forward which is resolved by means of the Finite Element Method (F.E.M.). Comparing the calculated results with those of experiments, satisfying agreement is found. It might be valuable for some practical applications and for the development of theory.