A regiospecific method for the aminobromination of β-nitrostyrene derivatives with acetamide and NBS as aminobrominating agent catalyzed by K3PO4 has been developed in acetone. The method can conveniently and efficiently convert β-nitrostyrenes into vicinal haloamines at room temperature in good yields up to 79 % and without the protection of an inert gaseous atmosphere. Strong electron-donating substituents(e.g.,OCH3) on the 4-position of benzene ring deactivated the reaction activity of β-nitrostyrenes and afforded a sole vicinal haloamine compound. Whereas strong electron-withdrawing substituents(e.g., NO2) activated reaction activity of them remarkably and afforded a sole vicinal haloamine compound, too. The result revealed that the addition reaction has an nucleophilic addition feature. The aminobromination of 14 examples of β-nitrostyrenes have been investigated in this work and the structure of all products were confirmed by their corresponding 1H NMR, 13C NMR spectra and their elemental analysis. A possible mechanism involving a nucleophilic conjugate addition was proposed.