MSRV-IN-1 (Compound M3) is an inhibitor targeting aquatic rhabdoviruses, including MSRV, SVCV, and IHNV, with IC50 values of 0.92 μM, 2.92 μM, and 2.78 μM, respectively. Instead of acting directly on virus particles, MSRV-IN-1 disrupts the replication environment by altering the virus-induced S-phase cell cycle arrest, inhibiting viral replication. Administered via intraperitoneal injection at a dose of 20 mg/kg, MSRV-IN-1 significantly improves the survival rate of MSRV-infected largemouth bass by 35.98% and reduces viral load in the liver, spleen, and kidneys. MSRV-IN-1 is applicable in research on rhabdovirus-associated diseases in aquaculture.