The invention discloses a diazo dye compound with improved application characteristics, excellent performance and low synthesis cost, a black dye thereof and a black ink composition. The diazo dye compound has a structural formula (I) or (II). In the formula, R1 is -SO3M or -COOM, R2 is -NO2, -H, -SO2CH2CH2Z and the like, Z is selected from -OH, -N(CH2CH2OH)2, -NHCH2CH2OH, -SCH2COOM, -SCH2CH2CH2SO3M, -NHCH2CH2COOM, -NHCH2COOM and the like, and M is positive ion. The black dye and the black ink composition have high light resistance, gas resistance and water resistance, and can be used to print high-quality image prints.