The magnetic and transport properties of epitaxial La0.7Ba0.3MnO3 films on LaAlO3 substrates have been investigated and compared with those on SrTiO3 substrates. It is found that the ferromagnetic and metallic transition temperature of the highly compressive strained films on LaAlO3 substrates decreases steadily with decreasing film thickness, while it changes little in the lightly strained films on SrTiO3 substrates. The properties of the films on LaAlO3 substrates are more sensitive to a post-annealing procedure. A tendency to phase separation, which induces a difference between the insulator-metal transition temperature T-MI and the Curie temperature T-C, is observed for the films with a medium oxygen annealing process. We argue that the phase separation is due to both the highly compressive strain and oxygen deficiency in the films. (c) 2010 Elsevier B.V. All rights reserved.