The bioelectrical impedance method was used to measure the body composition of 23352 adults (10070 males and 13282 females) from the minorities in China. This paper is to understand the current status of fat percentage and muscle mass in Chinese minorities, and to explore the changes in body composition with age. We found that males and females are generally overweighted, but not reached the level of obesity yet. Compared with the southern male ethnic groups, the males of northern Altaic languages ethnic groups have higher limb fat percentages, higher visceral fat levels and lower water percentages. Among the southern ethnic groups, the Tibeten-Burman languages ethnic groups, the Miao-Yao languages ethnic groups and the Zhuang-Dong languages ethnic groups have relatively close limb fat percentage, visceral fat level and water content. The South Asian languages ethnic groups has a large difference with these three southern ethnic groups. Compared with southern female ethnic groups, females from the northern Altaic languages ethnic groups have large torso and limb muscles and heavy bones. The female torso and limbs of the four southern ethnic groups have smaller muscle mass and lighter bones, which are close to each other. With age increases, male’s bone mass decreases, and water content increases, and upper extremity fat rate decreases, and trunk fat rate increases, and visceral fat levels increase, and fat concentrates in the trunk, and overall body fat rate increases. The muscle mass of the lower limbs of the male is reduced, and the muscle mass of the trunk is reduced, which ultimately leads to a decrease in the total muscle mass of the whole body. With age increases, the female’s fat rate and muscle mass of the upper extremities did not change significantly, the fat rate of the lower extremities decreased, the trunk fat rate and visceral fat level increased, the overall fat rate increased, the trunk muscle mass decreased, and the total muscle mass decreased. The cut-off point for male’s presumed decline in bone mass is 50 years old, and female is 60 years old. The cut-off point for a decline in total muscle mass in male is 40 years old, and female is 50 years old. The cut points for increasing the body moisture rate of males and females are all 60 years old, the cut points for increasing the visceral fat level are all 30 years old, the cut points for decreasing the total fat rate are all 60 years old, the cut points for increasing the body fat rate are 30 years old, and the cut-off points for torso muscle mass are 40 years old. We also found that body fat rate, visceral fat level and blood glucose levels were significantly positively correlated. The results of this paper basically reflect the basic laws of the changes in body composition from youth to the elderly.