Frequency　scanning　interferometry　(FSI)　with　an　external　cavity　diode　laser　is　an　effective　technique　for　measuring　the　absolute　distance　of　a　target.　However,　because　of　the　nonlinearity　in　optical　frequency　scanning,　an　interference　signal　becomes　a　non-stationary　chirp　signal,　which　is　a　critical　issue　to　extract　the　phase　of　the　interference　signal　for　improving　the　accuracy　of　FSI.　In　this　paper,　a　method　for　extracting　the　phase　using　complex　shifted　Morlet　wavelet　is　proposed　to　accurately　track　the　instantaneous　phase　of　the　chirp　signal,　and　the　selection　of　the　wavelet　parameters　is　also　derived.　The　method　is　verified　to　be　effective　and　stable　by　performing　simulations　and　experiments.　The　experimental　results　demonstrate　that　the　relative　error　of　the　phase　extraction　in　the　fractional　part　of　interference　signal　is　＜　1.5%;,　and　the　standard　deviation　of　absolute　distance　measurement　is　＜1.69　mu　m