This is a randomized, double-blind, placebo-controlled, parallel-group trial conducted in infants and young children aged 1 to 36 months with RSV infection.

A total of 498 subjects are expected to be enrolled and randomly assigned to the investigational product group or the placebo group in a 2:1 ratio; Administration will be based on the subject's weight, with a dose of 20 mg/kg three times daily for 5 consecutive days (15 doses).

Inclusion Criteria:

1. Infants and young children aged ≥ 1 month and ≤ 36 months, regardless of gender;
2. Weight ≥ 2.5 kg and ≤ 20 kg;
3. Positive RSV antigen or nucleic acid test
4. Duration of illness due to RSV infection ≤ 96 hours;
5. Presence of tachypnea and wheezing;
6. Wang Bronchiolitis Score≥ 5;
7. For subjects aged < 12 months, head circumference should be within the normal range corresponding to their age and gender.

Exclusion Criteria:

1. Subjects who have received protocol-specified prohibited medications:
2. Subjects with severe intrapulmonary complications or extrapulmonary complications;
3. Subjects requiring vasopressors or inotropic agents;
4. Subjects with known concurrent SARS-CoV-2 infection, influenza virus infection, Mycoplasma infection, or suspected concurrent bacterial or other pathogen infections;
5. Subjects with a known history of hypercapnia;
6. Subjects with chronic or persistent feeding difficulties;
7. Subjects with gastrointestinal diseases that the investigator believes may significantly affect the absorption of the study drug;
8. Subjects with congenital metabolic abnormalities;
9. Subjects with bronchopulmonary dysplasia requiring assisted ventilation or clinically significant congenital respiratory tract abnormalities;
10. Subjects with congenital heart disease (CHD) that the investigator assesses may affect efficacy evaluation;
11. Subjects with clinical evidence of hepatic decompensation; or abnormal liver function tests;
12. Subjects with renal failure, including renal abnormalities potentially related to renal insufficiency or abnormal renal function tests;
13. Subjects with a known history of HIV positivity, or suspected to be HIV positive by the investigator;
14. Subjects with known or suspected primary immunodeficiency diseases or transplant recipients;
15. Subjects with a history of epilepsy or febrile convulsions;
16. Subjects with a personal or family history of severe allergies or allergies;
17. Subjects with active or uncontrolled respiratory, cardiac, hepatic, central nervous system, or renal diseases, or other medical conditions deemed unsuitable for enrollment by the investigator;
18. Subjects who participated in other drug or medical device clinical trials and received investigational products or devices;
19. Subjects deemed unsuitable for participation in this study by the investigator for any other reason.