Objective: To investigate the association of D-dimer (DD) level on admission with the hospital length of stay (LOS) for the children with community-acquired pneumonia (CAP). Methods: The children diagnosed as CAP hospitalized in the Second Hospital of Tianjin Medical University from December 2016 to December 2017 were studied. The clinical and biological variables were retrieved via electronic medical record system. Binary logistic regression model and Cox proportional risk model were constructed to estimate the assosiation of DD level with hospital length of stay(LOS). Results: A total of 413 children met the inclusion criteria. Their median of LOS was 7 days (range from 3 to 21 days). The median of DD level on admission was 510.87 ng/mL and tertiles were 400 ng/mL and 712.23 ng/mL. In logistic regression model, both the high (＞712.23 ng/mL) and middle (400-712.23 ng/mL) DD level groups were in more risk for hospital stay of more than 7 days in comparison with the low DD level group (＜400). The OR values were 3.335 (95%CI:1.973-5.637, P＜0.001) and 2.015 (95%CI:1.195-3.398, P=0.009) respectively. Consistently, in Cox model high level of DD was associated with low probability of discharge (HR=0.652, 95%CI: 0.486-0.874, P=0.004 ), suggesting more risk of prolonged LOS in contrast to the low DD level group. Conclusion The DD level on admission should be independently associated with the hospital length of stay, suggesting the consideration of DD levels may be helpful for clinical management of the hospitalized children with CAP.