Objective To study the stability of vitamin C in health food and nutrition supplements at different dosages and forms. Methods The study was conducted in an artificial climate box based strictly on the requirement for hygienic stability of health food. Iodometric analysis with an automatic electric potential titrimeter was used according to the method in Chinese Pharmacopoeia (version two, 2010). Results The content of vitamin C in samples was determined once a month for three months. The declining ratio of vitamin C was from -7.29% to 94.26 % and the declining curves were drawn. Conclusion The contents of vitamin C in most health foods and nutrition supplements have declined at different levels after preservation for 3 months under the temperature of 37℃ and the humidity of 75%, especially in health food added with trace elements. The stability of vitamin C in health food and nutrition supplements can be significantly influenced by iron and calcium, while the influence of zinc is little. Ingredients and packing methods of samples are the main factors for the stability of vitamin C.