The effect of long-range interactions on the spontaneous polarization and the Curie temperature of the ferroelectricfilm is investigated by use of the Landau theory. On the assumption that the nearest-n eighbour interaction remains constant, we find that the spontaneous polarization and the phase transition temperature increase with the enhancement of the long-range interactions. In the case of positive extrapolation length, the critical thickness of the ferroelectric film,in which a size-driven phase transition occurs, decreases with the enhancement of the long-range interactions.