Objectives: This study aimed to study the difference of dental arch size of deciduous dentition between boys and girls in Beijing, the developmental tendency of dental arch from three to five years old, and the relationship between dental arch size and stature. Methods: Plaster models of primary dentitions taken from 143 children (71 boys and 72 girls) aged three-five were involved in this study. These children were healthy and had no malocclusion or bad oral habit. The models were divided into six groups according to the age (three, four, and five years old) and gender. The width, length, height and perimeter of the dental arch, children's height and weight were measured. Data were analyzed by using SAS soft package. Results: 1. In this study, the average width of primary dental arch (primary canines and second primary molars) of boys was larger than girls (p<0.001), and there was no difference in the length of dental arch. 2. There were positive correlation between the width of dental arch and children's height/weight (p<0.01), the perimeter of dental arch and children's weight (p<0.01). 3. The perimeter of dental arch in five-year-old group was shorter than three-year-old group (p<0.05), the average difference was 1.5mm. 4. There were no significant difference in the width and length of dental arch among each age group. Conclusion: In this study, the boys' dental arch was wider than the girls', and the dental arch size was positively related to the stature. The perimeter of dental arch was significantly reduced from three year old to five year old.