Using the full-potential linear-muffin-tin-orbital programs and the linear-response linear-muffin-tin-orbital programs，we calculated the electronic band structure, phonon spectrum and electron-phonon coupling strength in MgB2 film, and studied the effect of tension of MgB2 film on its superconductivity. It is shown that the softening of E2g phonon frequency, enchancement of the electron-phonon coupling and the phonon logarithm average frequency with contraction of the lattice constant along c-axis and elongation along a-axis resulted in the increase of superconducting transition temperature Tc. Our results are in good agreement with corresponding experiment.