Aiming at the problems of limited analysis and difficult validation on flow characteristics of children upper airway, this paper presents an experimental bench using upper airway models manufactured by 3D printing technology to study these problems. The maximum difference between experimental results and clinical nasal resistance test is 11.1%, which proves the experimental method based on 3D printing technology is reliable and accurate, and it can be a direct and easy method for the research of flow characteristics of children upper airway. After that, the effect of different levels of hypertrophy of tonsil on flow characteristics is studied. It is found that, when the narrow level of oropharynx reaches 56%, where the level of hypertrophy of tonsil reaches III degree, flow characteristics of upper airway will obviously change, in terms of increasing flow velocity and resistance, decreasing flow volume, and a large inverse pressure and pressure difference in oropharynx, which can an explanation of the symptoms for OSAHS child, and also will be a significant reference to clinicians on tonsillectomy operation and its postoperative recovery plan.