Five-year-old girl appeared breast development, there is the possibility of precocious puberty, parents need to go to the hospital for the child’s sex hormones and breast ultrasound examination, to exclude endocrine diseases after regular monitoring, if found endocrine tumors, if necessary, need to carry out surgical treatment. A five-year-old girl with breast development may have precocious puberty. At this time, endocrine diseases should be ruled out first, and parents can take their children to the hospital for breast ultrasound and sex hormone level examination. If no pathological abnormality is found in the breast ultrasound and the sex hormone level is physiologically elevated, endocrine diseases can be ruled out and the child can be observed regularly. If there are endocrine tumors, such as adrenal tumors, surgical treatment is needed. When a five-year-old girl develops precocious breast development, she needs to seek timely medical attention. Parents can avoid letting their children ingest foods or health products containing hormones, and at the same time ensure that their children have sufficient nutrition and sleep, choose appropriate underwear, and carry out regular observation and monitoring.