Abstract: According to the phenomenon that a trace amount of vanadium (V) can strongly catalyze the oxidation of Magenta red by potassium bromate to discolor in a dilute phosphoric acid medium with the existence of ascorbic acid, a new catalytic kinetic method for the ultratrace vanadium determination is established, which has the highest sensitivity among similar methods. Its linear range is: 0.0～400.0 pg/mL, the detection limit is 27 pg/mL. The influence factor of catalytic reaction rate and optimal experimental conditions, were investigated and determined. The catalytic reaction kinetic parameters are: apparent activation energy E0＇= 170.1 kJ/mol, apparent reaction rate constant k＇= 2.8×10^-3s^-1, the dynamics speed equation: －dC_MR/dt＝K＇·C_MR·C_KBrO3·C_Vc·C_V（Ⅴ） has been established. After studying the interaction of 25 coexistent ions, it was discovered that the majority of common ions do not interfere. The method has been used to determine ultratrace vanadium in the environmental at water. The relatively standard deviation was 1.65%~2.03%.