Objective <p>To evaluate the efficacy and safety of inhaled ambroxol solution in improving sputum of lower respiratory tract infections (LRTIs) in children.</p> Study Design <p>This study was a randomized, double-blind, parallel-group, placebo-controlled, multicenter trial. The patients were administered inhaled ambroxol or a placebo twice a day for 7 days. And researchers collected efficacy and (or) safety indicators every day during the course.</p> Results <p>A total of 236 children were randomly assigned to receive ambroxol or placebo (1:1). At all visit points after the medication, the mean difference of cough score with the baseline between the two groups was statistically significant (P &lt; 0.05). Compared with the baseline, the phlegm-sound scores in the throat of the experimental group decreased more on the 1st, 2nd, and 3rd days after administration (P &lt; 0.05). But there was no difference in pulmonary rale scores. The occurrence of adverse events in the experimental group was lower (21.37% vs. 35.59%, P = 0.021), and the incidence of adverse reactions was similar between the two groups (2.56% vs. 5.08%, P = 0.499).</p> Conclusion <p>Inhaled ambroxol solution could improve the sticky sputum symptoms in children with LRTIs and is safe in clinical application. Further research is needed to confirm these findings.</p> Trial registration <p>The study was retrospectively registered on June 14, 2023, at <a href="https://www.chictr.org.cn/">https://www.chictr.org.cn/</a> under the number ChiCTR2300072466.</p>