Twelve azophenol dyes were prepared by the tandem reaction of diazotization and coupling, using continuous flow chemistry technology with phenols, arylamines and sodium nitrite (molar ratio of 1:6:6) as starting materials, in a mixed solvent of ethanol and water, and with trifluoroacetic acid as a promoter. In substrate universality studies, it was demonstrated that both unsubstituted aniline and various electron-donating aromatic amines could efficiently undergo diazotization and subsequent coupled with 2-naphthol and resorcinol under mild reaction conditions. A series of azophenol dyes were obtained in the isolated yields of 76%~99% under optimized continuous flow conditions (0.04 mL/min flow rate) for 4.2 hours. The structures of the products were characterized and confirmed by nuclear magnetic resonance (NMR) spectroscopy. The stability operation experiment shows that this synthesis scheme has high stability and certain industrial application prospects. The traditional batch synthesis process has many problems. For example, diazonium salts are unstable and prone to decomposition, the temperature of the reaction system is difficult to control, there is an explosion risk, the synthesis efficiency is low, and the operation is cumbersome. In this method, after the diazonium salt was generated in the microreactor, it is in situ coupled with phenolic compounds to obtain azophenol dyes, avoiding the explosion risk caused by the large-scale generation of unstable diazonium salts and the drawback of producing by-products. At the same time, the use of green solvents reduces the environmental pollution risk, can simplify the process, reduce the cost, and improve the synthesis efficiency.