Objective: To observe the efficacy and mechanism of the treatment of children with allergic asthma complicated with allergic rhinitis with sublingual immunotherapy combined with loratadine. Methods: Eighty cases of children with allergic asthma complicated with allergic rhinitis were selected and divided into a combined treatment group and a standard treatment group according to the method of random numbers. The standard treatment group was treated with loratadine, and the combined treatment group was treated with sublingual administration of dust mite drops combined with loratadine. Before and after the treatment for 3 months, the severity of asthma and rhinitis, pulmonary ventilation function of the patients were evaluated; the immune factors, T lymphocyte subgroup and inflammation index between the two groups were compared. Results: Before the treatment, the asthma symptom scores, rhinitis symptom scores, pulmonary ventilation function, immune factors, T lymphocyte subgroup and inflammation index had no statistical significance (P>0.05); after the treatment, asthma symptom scores and rhinitis symptom scores were significantly lower than those before the treatment (P<0.05), and the scores in the joint treatment group were significantly lower than those in the standard treatment group (P<0.05); FEV1, FVC and PEF were significantly higher than those before the treatment in the two groups (P<0.05), and the levels in the combined treatment group was significantly higher than those in the standard treatment group (P<0.05). IFN-γ level was significantly increased in both groups, and IL-4 and Il-17 levels were significantly decreased (P<0.05), the changes in the combined treatment group were more significant than those in the standard treatment group (P<0.05). IgE level was significantly decreased and IgG4 level were significantly increased in both groups (P<0.05), and the changes were more significant in the combined treatment group when compared with the standard treatment group (P<0.05). CD3+, CD4+ and CD4+/CD8+ levels were significantly increased and CD8+ levels were significantly decreased in the two groups (P<0.05); the changes were more significant in the combined treatment group when compared with the standard treatment group (P<0.05). Conclusion: Sublingual dust mite drops combined with fratadine in the treatment of pediatric allergic rhinitis with asthma has a significant effect.