Auramine-O (Au-O) dye is an imine type colorant which is used in many industrials such as food, textile, leader, printing, optic, biomedical, laser and so on. In spite of its spread applications, Au-O dye is toxic and resistant in the environment, aquatic organisms and human body. Hence, it’s using is banned in many countries. Consequently, identification and determination of Au-O is a necessary routine work in Analytical chemistry. On the other hand, there are many unanswered questions about Au-O dye’s behavior in aqueous solution at different acidity and concentration for using it in other applications which we attempted to address here. Hence, in this work, Au-O dye’s absorbance, fluorescence and aggregation behaviors were revisited. We showed that Au-O dye forms J-aggregate macromolecule in very acidic aqueous solution (pH=0.5) and high concentration (10-2 M) as red color solution with a λmax=295 nm and a shoulder peak located at 537 nm in UV-vis. spectrum. This molecular J-aggregate showed fluorescence emission at λmax=537 nm which has not been reported, so far. A Stokes shift of 120 nm for J-aggregate indicates that this dye is likely to be a suitable candidate for fluorescent microcopy and does not suffer from low signal-to-noise ratio and self-quenching problems. We also showed that using the Stephen’s reduction reaction, Au-O can be converted directly to corresponding colorless Michler’s ketone without oxidative complextation. Finally, we reveal that fluorescence of Au-O has been unchanged by a magnetic field.