A simple and rapid method for the measurement of vitamin C in vegetables and fruits by a commercial glucometer equipped with slightly modified electrode strips was proposed. The simply methanol-pretreated disposable strip electrodes retained excellent electrocatalytic activity towards the oxidation of vitamin C and exhibited the capability of resisting interference from other electroactive species presented in the plants. The established method was successfully applied to determination of vitamin C in real samples. Under the optimum conditions, the linear range was from 0.1 to 2.5 mg/mL with the detection limit of less than 0.1 mg/mL. The results showed that the treated commercial strips can be used as a sensitive, selective, and low-cost sensor for amperometric determination of vitamin C in food plants. The proposed method expanded the application of the hand-held device from blood glucose test to the evaluation of the level of vitamin C in food plants.