The age boundary line between children and adults is thirteen. Before thirteen, children all wear long gown. Until thirteen, after rites of "wearing trousers" or "wear skirt" is held, that is after the puberty rite, can they change their clothes and join the ranks of adults.

The puberty rite of Pumis is often held on Big New Year's Day (spring festival). The rite is mostly directed by the mother or mother's brother, which is simple but enthusiastic. When the time comes, members of the family sit around the fire pit with raging flames, and look attentively at the scene with a feeling of joy: the child walks by the magical post near the fire pit, and steps on pig's fat and grain bag. The fat of pig symbolizes wealth and the grain bag stands for bumper harvest, which means he or she will have food to eat and clothes to wear when he or she grows up and live a happy life. If the child is a boy, he should hold a sharp knife in the right hand and a silver coin in the left hand. The silver coin symbolizes wealth and the sharp knife symbolizes bravery. If the child is a girl, she should hold adornments like earrings or bracelet in her right hand and yarn or cloth of flax in her left hand, which stands for family right that she can enjoy and work obligations that she should assume. Then the wizard prays to kitchen god and ancestors, the mother's brother or mother takes off his or her long gown and dresses him or her with short coat and long trousers or plaited skirt. After the clothes are changed, everybody presents him or her some gifts to show their congratulations. The fellow or girl should kowtow and offer wine to thank the kitchen god and relatives one by one and hopes to get their protection and help in the future life journey. From then on, the adult fellow or girl can take part in collective productive labor and all kinds of social intercourse.

It is said the custom of "wearing trousers" or "wearing skirt" held by the Pumis for children who are thirteen is of long standing. According to legend, when Hubilie attacked Yunnan, there were two only thirteen years old boys who went to the South with the army when he passed the western Sichuan. The two boys went through fire and water, were brave and skillful in battle and were appreciated deeply by Hubilie. Later, in order to commemorate them and also educate younger generations, people hold puberty rite for children who are 13 to bless that they could grow up healthily and become a person with lofty ideals. From then on, this activity was carried on as a custom and has been handed down till now.