Spirulina is an alga rich in high-quality protein and carotenoids. It is unclear whether spirulina can improve the total-body vitamin A stores of school-age children in China with a high prevalence of vitamin A malnutrition. We aimed to evaluate the efficacy of spirulina in improving the total-body vitamin A stores of school-age children in rural areas of China when they consumed spirulina in their daily meals. A total of 228 children (6–11 years) were recruited and randomly divided into three groups supplemented with 4 g (containing 4·18 µg β-carotene), 2 g (containing 2·54 µg β-carotene) or 0 g spirulina 5 d/week for 10 weeks, respectively. Before and after the intervention period, each child was given 0·5 mg [2H4]retinyl acetate and [2H8]retinyl acetate, respectively. To assess vitamin A stores, blood samples (3 ml) were collected on the third and the twenty-first day after each labelled retinyl acetate dose for a retinol enrichment analysis using a GC mass spectrometer. The concentrations of retinol and β-carotene in serum samples were also determined by using HPLC. After the 10-week intervention, serum β-carotene concentrations of children with 2 or 4 g spirulina supplement increased by 0·160 and 0·389 µmmol/l, respectively. Total-body vitamin A stores increased significantly, with a median increase of 0·160 mmol in children taking 2 g spirulina and of 0·279 mmol in children taking 4 g spirulina. Spirulina is a good dietary source of β-carotene, which may effectively increase the total-body vitamin A stores of Chinese school-age children.