Abstract: Thermal properties of multilayered thin films deposited on substrates are influenced by each layer,so it is important to estimate simultaneously the property of each layer of them.Laser induced transient thermal grating technique provides higher sensitivity and depth resolution in photothermal and photoacoustic investigations for spatially restricted areas near surface.In this paper,the thermal diffusivities of bilayered thin films with nanoscaled thickness deposited on substrates are characterized by transient grating method.Based on the experimental results of the laser induced transient thermal grating technique,a two-dimensional thermal diffusivity model and finite element method are proposed to calculate the thermal diffusivities of the trilayered structures.By fitting the theoretical calculations to the experimental data of a series of trilayered structures of Al/ZnO/Si with different thicknesses of ZnO films,the thermal diffusivities of the Al and ZnO films can be evaluated simultaneously.