Objective To study the body density of thirteen Mongolian groups, to compare their gender and ethnic differences, and to investigate the correlation between the body density and longitude, latitude, annual average temperature and age. Methods The triceps skinfold and the subscapular skinfold were measured. Jinji, Changling formula was used to calculate the body density of thirteen Mongolian groups. Results In the thirteen Mongolian groups, the body density of Yunnan Mongolian was the largest, and that of Ejina Torghut Mongolian was the least. The differences of the Mongolian body density among ethnic groups, gender, age groups and 4 regions were statistically significant. The body density of Mongolian had a significant negative correlation with longitude and age. Conclusion The body density of the southern Mongolian is greater than that of the northern Mongolian, and the body density of the western Mongolian is greater than that of the eastern Mongolian.