A virus was successfully isolated from a sick cat exhibiting clinical signs such as oral mu-cosal ulceration,nasal mucosal redness,and increased nasal secretions utilizing F81 cells.Through a comprehensive analysis as such PCR amplication,sequencing,morphology,serology,and animal re-gression tests,the virus was identified as a feline calicivirus and named FCV-BJ,an inactivated vac-cine was developed from this isolated strain its safety and efficacy were assessed.The results re-vealed that the isolated FCV-BJ strain exhibited characteristic serological and morphological fea-tures consistent with caliciviruses.Furthermore,inoculation of cats with the FCV-BJ demonstrated the strain is highly virulent and the cats manifested the clinical signs of feline calicivirus infection.For the vaccination trial,domestic cats were immunized with inactivated fifth-generation virus cell culture at varying dilutions,followed by a booster immunization after 21 days.Fourteen days after the challenge with the virus,cats immunized with 107.0 TCID50/mL or higher remained largely healthy,while all cats in the control group developed clinical signs of FCV.These findings suggest that the inactivated vaccine derived from the FCV-BJ isolate exhibits strong immunogenicity and protective efficacy at a minimum immunization dose of 107.0 TCID50/mL.This strain holds promise as a candidate for vaccine production,providing a valuable reference and foundation for future re-search and development of feline calicivirus vaccines.