The invention discloses a kit for predicting adolescent obesity in childhood and an application thereof. The invention provides an application of a substance used for detecting the abundance of target bacteria in intestinal flora of children to be detected in preparation of products for predicting simple obesity of children, and the target bacteria are any one of Firmicutes, Clostridia, Clostridiales, Clostridiaceae, Clostridium, Bacteroidetes, Bacteroidia, Bacteroidales, Bacteroidaceae, Bacteroides, Oscillospira, Coriobacteriaceae and Collinsella. Specific information is obtained from a simple obesity queue of children to better embody the intestinal flora features of obesity of children, and by monitoring the abundance change of the characteristic species, the development and change of the obesity state can be predicated; the obtained intestinal flora features of obesity of children are compared with the intestinal flora features obtained by researching other diseases to further predict the risk and trend of related obesity diseases.