In this paper, the bioelectrical impedance analysis was used to measure body composition of Jing peoples in Guangxi. In December 2020, the research team measured 16 indicators of 430 Jing adults (182 males and 248 females) in the “Three Islands of Jing” in Dongxing City, Guangxi Zhuang Autonomous Region. The results show that mass, total body muscle mass, trunk muscle mass, estimated bone mass and total energy metabolism of Jing males and females are significantly negatively correlated with age. Changes in body composition with age are mainly caused by natural physiological changes with decreased labor intensity. The percentage body fat of males increases with age, due to increased trunk fat. The mass, total body muscle mass, estimated bone mass, total energy metabolism, percentage body water, and limbs and trunk muscle mass of Jing males are higher than those of females; while percentage of body fat and of limb and trunk fat are lower than those of females. Jing males possess a greater mass and a higher proportion of skeletal muscle in mass than females. These two last factors coupled with differences in labor intensity could result in discrepancies of body compositions of the two genders, including body muscle mass, bone mass and percentage body fat. Generally speaking, Jing adults are obese with high fat content but normal body water content. Their body composition characteristics are not similar to other Chinese ethnic groups of the same Austroasiatic languages or in the same coastal areas, but are relatively closer to those of Mongols in China, where mass, percentage of body fat and of body water are similar. Factors such as living environment, social economy, daily diet and labor intensity are the reasons for the higher mass and percent body fat of the Jing adults.