In recent years, goose gout, a severe infectious disease, has affected the development of the goose industry in China. Two different genotypes of goose astrovirus (GAstV), named as GAstV-1 and GAstV-2, were identified. GAstV-2 viruses are known to be the causative agent of goose gout; however, GAstV-1 has not been isolated, and the relationship between GAstV-1 and goose gout is unknown. One full genome sequence, designated as GAstV/CHN/TZ03/2019 (TZ03), was determined from the clinical tissue samples of a diseased gosling using next-generation sequencing. The complete genome of TZ03 was 7,262 nucleotides in length with typical genomic characteristics of avastroviruses. The TZ03 strain shares the highest identity (96.6%) with the GAstV-1 strain FLX, but only 51.5 to 61.3% identity with other astroviruses in Avastrovirus. Phylogenetic analysis revealed that the TZ03 strain clustered together with the GAstV-1 strains FLX and AHDY and was highly divergent from GAstV-2 viruses. The TZ03 strain was successfully isolated from goose embryos and caused 100% mortality of goose embryos after 5 passages. Electron microscopy showed that the virus particles were spherical with a diameter of ∼22 nm. The clinical symptoms were reproduced by experimental infection of healthy goslings, which were similar to those caused by GAstV-2 strains. Our data show that GAstV-1 is one of the causative agents of the ongoing goose gout disease in China. These findings enrich our understanding of the evolution of GAstVs that cause gout and provide potential options for developing biological products to treat goose gout.