The room temperature electrocaloric effect is researched for (110) oriented KNbO₃ film based on Landau-Devonshire theory. The phase map with different ferroelectric states is built at room temperature with the considerations of thermodynamic equilibrium conditions and minimum of thermodynamic potential. Five ferroelectric structural phases are obtained theoretically. The negative in-plane misfit strains are conducive to form the tetragonal c phase and the positive strains are in favor of the stability of tetragonal a1 and a₂ phases. The electrocaloric effect relies on both misfit strain and electric field. Moreover, large electrocaloric effect is achieved in the orthorhombic phases.