The　electron　spin　resonance　(ESR)　spectra　of　electron-doped　La0.9Sb0.1MnO3　with　colossal　magnetoresistance　effect　have　been　studied　in　this　paper.　The　ESR　results　demonstrate　that　there　is　magnetic　phase　separation　and　complex　magnetic　structure.　The　compound　changes　from　ferromagnetic　to　paramagnetic　state　gradually　with　increasing　temperature.　Ferromagnetic　and　paramagnetic　phases　coexist　in　the　wide　transitional　temperature　range.　The　ESR　absorption　spectra　have　been　fitted　by　Lorentzian　curves　and　the　magnetic　phase　evolvement　with　temperature　has　been　analyzed.