Kinetics and Mechanism of $N_2H_4-KBrO_3$ reaction in the presence of allyl alcohol have been studied. The pseudo-first order rate constant for gas evolution was found to be $10^{-4}{sim}10^{-2};sec^{-1};at;25.0{pm}0.1^{circ}C$, increasing with concentration of hydrogen ion. When concentrations of sulfuric acid and allyl alcohol are both sufficiently high, the following overall reaction explains experimental results reasonably well: $N_2H_4;+;BrO_3^-;+;H^+;{ o};N_2;+;HOBr;+;2H_2O,;CH_2;=;CHCH_2OH;+;HOBr;{ o};CH_2-OHCHBrCH_2OH$. More complicated reaction mechanisms at lower acidity conditions have been contemplated.