Study done in 2012- 2013 to estimate calcium requirement in children aged from 3-5 years, using calcium balance method. Total of 30 children participated in study. Each participant was subjected to a low calcium intake (300 mg/ day) for 15 days. After an interval of 2 weeks, another 15 days period was set with high calcium intake (600 mg/ day) for each subject. Calcium intake levels were calculated based on Vietnamese Food Composition Table. Calcium content in intake, feace and urine were analyzed by Atomic Absorption Spectrophotometer. Calcium retention was calculated at each dose of calcium intake. Calcium requirement was estimated by linear regression between calcium intake and calcium retention. The results showed that calcium intake level at 140 mg/day of Ca retention was 378 mg/day in studied subjects. Recommended dietary allowance (RDA) for calcium is 450 mg per day children aged from 3-5 years old.