Primary osteoporosis is a common metabolic disease in China, causing immense disease and economic burden to patients, their families and the society. Prevention is an important strategy to reduce the disease burden of primary osteoporosis. Calcium, as a basic element for maintaining bone health, plays an important role in the prevention of primary osteoporosis. This guideline was initiated by the Chinese Pharmaceutical Society Evidence-based Pharmacy Specialised Committee. The standard methodology for the development of evidence-based clinical practice guidelines of the World Health Organization (WHO) was employed. A multidisciplinary guideline working group was formed. Delphi method was used to select and eventually identified 15 key clinical questions. Systematic evaluation was carried out on each of the key clinical question and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to formed 15 recommendations, providing guidance for standardizing the clinical practice of calcium supplementation in prevention of primary osteoporosis in adults in China.