This work proposed an equivalent layer for thermal characteristics of interdigital transducers (IDTs) based on the definition of thermal resistance of heat transfer. The equivalent layer is modeled with the derived anisotropic equivalent thermal conductivities at X, Y and Z directions. To validate the equivalence, a simulation procedure with two discrete steps was carried out, and the temperature distribution at steady state was confirmed to be the same between the unit cell model with the equivalent layer and the unit cell model with conventional real structure of IDT layer. Lastly, a 3D full-size model of a filter consisting of seven resonators was simulated for observation of the self-heating effect.