Respiratory syncytial virus (RSV) is a ubiquitous respiratory virus that affects individuals of all ages; however, there is a notable lack of targeted treatments. RSV infection is associated with a range of respiratory symptoms, including bronchiolitis and pneumonia. Baicalin (BA) exhibits significant therapeutic effects against RSV infection through mechanisms of viral inhibition and anti-inflammatory action. Nonetheless, the clinical application of BA is constrained by its low solubility and bioavailability. In this study, we prepared BA nanodrugs (BA NDs) with enhanced water solubility utilizing the supramolecular self-assembled strategy, and we further conducted a comparative analysis of this pharmacological activity between free drugs and NDs of BA. Both in vitro and in vivo results demonstrated that BA NDs significantly enhanced the dual effects of viral inhibition and inflammation relief compared to free BA, attributed to prolonged lung retention, improved cellular uptake, and increased targeting affinity. Our study confirms that the nanosizing strategy, a straightforward approach to enhance drug solubility, can also increase biological activity compared to free drugs with the same content, thereby providing a potential ND for RSV treatment. This correlation analysis between the existing forms of drugs and their biological activity offers a novel perspective for research on the active ingredients of traditional Chinese medicine.