【Abstract】Objective To investigate the clinical characteristics of children and adolescents with different subtypes of orthostatic intolerance（OI）and the hemodynamic characteristics of them in the head-up tilt test（HUTT）.Methods The retrospective study was performed to collect the medical records and HUTT result of 363 patients with suspected OI from 2014 to now. The clinical and hemodynamic characteristics of each subtype were analyzed. Results Statistical differences were evidenced in gender, occurrence time of positive signs and changes in hemodynamic parameters（P＜0.05）among children with different subtypes of OI. However, there were no significant differences in age and onset time of presyncope（P＞0.05）.The heart rate（HR）of POTS group increased rapidly but had little change in blood pressure（BP）. On the contrary, BP were significantly decreased compared with those before the experiment in patients with VVS. In the OHT group, BP increased rapidly especially diastolic blood pressure（DBP）.Both HR and BP increased significantly in patients with POTS combine OHT. In addition, patients with negative results accounted for 14.9%, statistical difference were observed in HR and BP changes after HUTT（P＜0.05）.Conclusion VVS and POTS are the main types of orthostatic intolerance, which occur commonly in female. Dizziness, chest tightness, and other symptoms are helpful for the diagnosis of OI, but not specific. Different subtypes have different clinical and hemodynamic characteristics. Children with suspected POTS, OHT, POTS combined with OHT can be given a head-up test first. If the child tolerates it, the observation time can be appropriately increased to distinguish combined type from monotype. Some children with negative screening results may belong to VVS.