A method for the determination of vanadium (V) in food by spectrophotometry was established. In the citric medium, vanadium (V) in food was determined according to the fading reaction of methyl violet by potassium periodate. The reaction medium and reagent dosage were studied. , reaction temperature and reaction time and other factors, simultaneously determine the apparent activation energy and apparent rate constant, and draw a working curve to determine the linear range and detection limit. Wet digestion and microwave digestion respectively to treat sweet potatoes, cucumbers and snow lotus The results were determined by spectrophotometry. The experimental results show that the determination wavelength is 583 nm. In citric medium, vanadium has a strong catalytic effect on the oxidation of methyl violet by potassium periodate. The best experimental conditions: 0.2 mol/L Citric acid 3.0 mL, 2× 10-2 mol/L potassium periodate 2.5 mL, 1.0× 10-4 mol/L methyl violet 3.0 mL, reaction temperature 90 °C, reaction time 10 min, The detection limit of the method was 1.98× 10-2μg/mL, the linear range was 0-1.0 μ g/(25 mL), the apparent activation energy of the catalytic reaction was 10.097 kJ/mol, and the apparent rate constant was 1.625× 10-3 s-1. Processing samples by microwave digestion High precision. Experimentally determined content of the samples did not exceed 120 mg / kg, sample vanadium (Ⅴ) contents are satisfactory.