Using　a　new　homodimeric　hydrophilic　indole　dye　(Dye-I)　as　fluorescence　probe,　a　sensitive　synchronous　spectrofluorometric　determination　for　protein　was　developed.　Characteristics　of　the　fluorescence　reaction　between　DYE-1　and　BSA　protein　were　investigated.　Effects　of　the　concentration　of　the　hydrophilic　dye,　pH　value　of　the　buffer　solution,　and　ion-intensity　of　NaCl　were　also　studied　and　the　optimum　condition　was　gained.　At　pH　of　2.50,　electrostatic　interactions　of　positive　charges　of　the　BSA　chain　and　negative　charges　on　the　sulfonic　groups　of　DYE-1　were　carried　out.　The　interactions　of　the　indole　group　of　DYE-1　and　some　active　groups　of　BSA　(viz.　amido,　carboxyl　or　sulfhydryl)　were　also　achieved,　and　resulted　in　the　combination　of　indole　group　of　dye　at　the　chain　of　BSA,　which　caused　a　notable　increase　in　synchronous　fluorescence　with　an　observable　shift　to　the　longer　emission　wavelength.　Effects　of　the　concentration　of　indole　dye　on　the　determination　of　BSA　were　also　investigated.　With　the　augmentation　of　BSA,　the　α-helix　structure　of　BSA　molecular　would　change　from　the　unwrapped　state　to　the　enfolded　state,　which　was　in　favor　of　restraining　free-oscillation　of　fluorescence　probe　in　the　solution　and　maintaining　a　high　energy　transfer　efficiency.　Such　a　fact　would　fuel　a　high　fluorescence　enhancement.　and　the　change　in　fluorescence　intensity　(Δ　F)　gained　the　peak　at　3.00molL-1.　The　influences　of　ion-intensity　of　NaCl　on　the　fluorescence　of　BSA-DYE-1　system　was　visible.　Effects　of　coexistent　substances　such　as　amino　acid　and　metal　ions　such　as　Cu2+,　K+,　Ca2+,　Mg2+,　Al3+,　and　Zn2+　were　also　investigated.　Most　substances　showed　no　notable　influences　on　the　determination　of　BSA　except　Zn2+　and　Cu2+　ions.　Under　the　optimum　conditions,　good　calibration　curves　of　the　protein　were　also　obtained　in　the　range　of　5.00　×　10-7-2.50　×　10-5　gmL-1　(BSA)　with　a　detection　limit　of　3　×　10-8　gmL-1.　Applied　to　simulant　protein　samples　at　the　level　of　1.00,　2.00,　and　5.00gmL-1　of　BSA,　the　recoveries　were　in　the　range　of　98.6%-103.0%　with　the　RSD　of　1.1%-1.9%.　Compared　with　the　UV　standard　method,　the　relative　deviation　was　obtained　in　the　range　of　0.4%-3.9%.