This paper introduces a kinetic method based on the oxidizing action of vanadate ion on 1,8-diamino-4,5-dihydroxyanthraquinone-2,7-disulfonic acid. The reaction between these two species is monitored spectrophoto-metrically at 602 nm. The kinetic parameters of such a reaction are also reported. The calibration graph has two linear segments in the ranges 2.5–4.5 and 7.3–50 μg/mL of vanadium, respectively. The interferences of foreign ions in the determination have been studied and the proposed method has been applied to the determination of non-volatile vanadium in two crude oils.