The fluorescence properties and fluorescence stability of 2，4，8，10-tetrabroitro-benzopyrido-1，3a，6，6a-tetraazapentylene （BPTAP） were comprehensively investigated. The spectral properties of BPTAP in different solvents （acetonitrile， methanol， tetrahydrofuran， acetone， trichloromethane， ethyl acetate， N"-N"-dimethylformamide， dimethyl sulfone）， content of water （0-100%）， pH （2.0-12.0） were studied in detail. The effects of light， temperature and pH value on the fluorescence stability of BPTAP solution were investigated， and the mechanism of fluorescence decay of BPTAP solution was analyzed by ultra performance liquid chromatography-high resolution mass spectrometry （UPLC-HRMS）. The results show that although BPTAP has four nitro groups， it exhibits strong green fluorescence in some organic solvents. The fluorescence intensity of BPTAP in acetonitrile is the highest， and its maximum absorption/emission wavelength is 460 nm/508 nm. Low content of water （≤10%） can increase fluorescence intensity of BPTAP， while high content of water （>10%） decrease the fluorescence of BPTAP sharply. BPTAP has higher fluorescence in acidic， neutral and weak alkaline conditions. When the pH value is above 9.0， the fluorescence of BPTAP decreases rapidly with the increase of pH value. BPTAP shows good stability in room temperature and natural light. The closer the light wavelength is to the maximum absorption wavelength of BPTAP and the higher the temperature， the worse the fluorescence stability of BPTAP. The increase of pH value not only reduces the fluorescence intensity of BPTAP， but also accelerates the decline of BPTAP fluorescence. The mechanism of fluorescence decay of BPTAP under alkaline condition is based on nucleophilic substitution. The nitro group at para site of pyridine ring is replaced by the hydroxyl group in alkaline solution to form a new compound 1 （the elemental composition ［M-H］^- is C₁₁H₃N₈O₇）.