A　new　method　based　on　order　tracking　technique　for　reducing　the　effect　of　nonlinear　optical　frequency　swept　in　frequency　sweeping　interferometer　(FSI)　is　presented.　The　main　factors　affecting　the　measuring　accuracy　of　the　FSI　system　are　discussed　in　frequency　domain.　This　method　utilizes　the　optical　resonant　characteristic　of　a　Fabry-Perot　etalon　to　measure　the　instantaneous　optical　frequency　of　a　laser　rapidly.　Carries　on　the　data　linear　fitting　to　the　optical　frequency　on　the　least-square　method　and　make　the　slope　of　the　linear　equation　as　the　correction　rate　of　optical　frequency.　The　time　series　of　equidistant　optical　frequency　grid　can　be　obtained　with　polynomial　fit　and　interpolation　of　optical　frequency.　The　interference　signal　can　be　resampled　according　to　time　series　of　equidistant　optical　frequency　grid,　and　then　reconstructed　by　using　data　interpolation.　The　frequency　value　of　non-stationary　interference　signal　is　achieved　after　spectral　analysis　of　reconstructed　interference　signal.　The　results　indicate　that　this　method　dramatically　reduces　the　effects　of　the　nonlinear　sweep　without　limit　the　range　of　the　measured　distance,　and　demonstrates　spatial　resolution　enhancement　of　more　than　36　times　in　the　range　of　1000　mm.　©　2016,　Chinese　Laser　Press.　All　right　reserved.