In this paper we present the results of positron annihilation doppler broadening spectroscopy (PADB), X-ray diffraction spectra (XRD), and atomic force microscopy (AFM) measurements on the undoped GaSb and Te-doped GaSb films grown on GaAs substrate by molecular beam epitaxy(MBE). Research shows that the S parameter is smaller in GaSb film than the bulk material. The defects in the Te-doped N-type semiconductor GaSb obtained by MBE are mainly vacancies and impurity atoms instead of complex defects.