Gradient thermal barrier coatings（gradient TBCs） composed of different mix ratio of thermal barrier coatings and substrate are used as intermediate layer in order to reduce thermal stress resulted from heat mismatch between two materials. Temperature gradient and thermal stress of gradient TBCs were numerically calculated by combining phonon scattering model（for gradient TBCs） and Fouier heat conduction model（for substrate). The effects of the thermal physical properties（relaxation time and phonon speed） on the temperature field, the influences of gradient distribution of the elastic modulus and coefficient of thermal expansion on thermal stress are discussed. It is concluded that in the gradient TBCs, maximal values of thermal stress, temperature gradient are lower than that in constant TBCs. The effect of the thermal expansion coefficient on thermal stress is greater than the effect of the elastic modulus on thermal stress.