In　the　nonlinear　polarization　rotation　(NPR)　mode　locking　fiber　laser,　the　electric　fields　of　different　intensity　of　pluses　will　have　different　nonlinear　phase　shifts　because　of　self　phase　modulation　(SPM)　and　cross-phase　modulation　(XPM)　effects.　In　this　paper　we　analysis　the　SPM　and　XPM　effect　on　the　characteristics　of　pulses　in　fiber　which　were　influenced　when　we　adjustment　the　wave　plates　in　the　NPR　fiber　lasers.　At　the　same　time,　we　discussed　the　pulses　waveform＇s　influence　caused　by　the　strength　of　the　SPM　and　XPM　in　fibers.