The present work uses two-temperature model and Cattaneo's constitutive model to study the thermomechanical responses and the size effect on energy transport during ultrafast laser heating of Au nanofilms. It is shown that the grain size effects on thermophysical properties, heat transport and thermal stresses are rather evident when the average grain diameter is less than the electron mean free path. The study on heat transport shows that there are two heat waves propagating in the lattice during nonequilibrium heating of films. It is found that the classical thermoelastic theory can not reveal the generation of the ultrafast thermal stresses during nonequilibrium heating: however, it can approximately describe the stress evolution in the stage of thermal equilibrium. (C) 2011 Elsevier B.V. All rights reserved.