Purpose To analyze the genetic and clinical features of children with MAP2K1-mutated Langerhans cell histiocytosis (LCH). Methods We compared the clinical features of 37 children with MAP2K1-mutated LCH with those of the BRAF(V600E) mutation group (n = 133) and no known mutation group (n = 59) in the same period. Results We found 13 mutations of the MAP2K1 gene, which were mainly concentrated at p.53-62 and p.98-103. The most common mutation site was c.172_186del (12/37). Compared with the BRAF(V600E) mutation group, the patients with MAP2K1 mutations were mainly characterized by single-system multiple bone involvement (P = 0.022), with later disease onset (P = 0.029) as well as less involvement of risk organs, especially liver (P = 0.024). There was no significant difference in clinical features compared with the no known mutation group. The 2-year progression-free survival rate of first-line treatment (ChiCTR1900025783, 07/09/2019) in MAP2K1-mutated patients was 65.6% +/- 9.5%. The prognosis of patients with lung involvement was poor [HR (95% CI) = 6.312 (1.769-22.526), P = 0.005]. More progression or relapses could be found in patients with bony thorax involvement (8/17 vs. 2/20, P = 0.023), yet involvements in other sites of bones, such as craniofacial bone involvement (8/26 vs. 2/11, P = 0.688) and limb bone involvement (5/12 vs. 5/25, P = 0.240), were not correlated to disease progression or relapse. Conclusion The children with MAP2K1-mutated LCH have specific clinical features requiring clinical stratification and precise treatment. MAP2K1-mutated patients with lung involvement (especially with bony thorax involvement) had poor prognosis.