To reexamine the authenticity of astronomical records in Samguk sagi, this paper analyzes two types of records in particular formats: 1) the records displaying dates by sexagesimal signs, and 2) the records informing the positions of astronomical phenomena regarding the constellations. My analysis shows that all records with sexagesimal date signs have corresponding records in Chinese historical books. This implies that the sexagesimal date signs were added to the original records, when Samguk sagi was compiled in 1145, using the information available in corresponding Chinese records. All records informing the positions of astronomical phenomena regarding the constellations, before the late 7th century of unification, except for two cases, have Chinese corresponding records. This implies that the constellations were also added, when Samguk sagi was edited, to the original records by adopting those positional information specified in the corresponding Chinese records.