ObjectiveTo summarize the characteristics of croup in children residing at ultra-high altitude.MethodsGeneral information, clinical manifestations, degree of laryngeal obstruction, vital signs, and blood test results, along with the treatment in 343 children with croup were collected and analyzed. Vital signs at admission were compared with those at discharge.ResultsAll children lived at an average of (4 010.30 ± 282.76) m above the sea level. In the 343 children with croup, the highest prevalence (64.14%, 220/343) was found in the first year of life, and 29.74% of them caught a fever with pneumonia. Degree Ⅰ laryngeal obstruction was found in 93.88% (322/343) of children, degree Ⅱ in 3.21% (11/343), degree Ⅲ in 2.92% (10/343), and no degree Ⅳ was found. In these children, the body temperature, heart and respiratory rates were all lower at discharge than at admission (95%CI: -0.67--0.50, -10.28--6.75, -2.11--1.46; P <0.001), whereas oxygen saturation was higher at discharge (89.17% ± 3.41% vs 86.80% ± 6.21%, P<0.001, 95%CI:1.64-3.09). No significant difference was found in red blood cell count between male and female children (P=0.853), but higher hemoglobin was found in male children than female children (P=0.044). The white blood cell counts and neutrophil counts in male children were all lower than those in female children (P=0.024, P=0.040). High incidence of croup was found in winter while low in summer.ConclusionsChildren less than 1 year old are more likely to caught a croup. They may suffer from fever due to pneumonia. Degree I laryngeal obstruction was most common in children with croup but they still require careful attention.