A comparative metabolomic analysis was performed using purple potato tubers and derived red mutant tubers to investigate the regulation of anthocyanin biosynthesis. The metabolome analysis revealed 19 key differential metabolites including 10 flavonoids and 4 nucleotides. As a differential metabolite, pelargonidin was responsible for the mutant, and other metabolites had a correlation with it. To further analyse the regulatory mechanism of the differential metabolites, correlation analyses of metabolome and transcriptome were done. Among the differential metabolites, seven flavonoids and F3′5′H were in the flavonoid metabolic pathway. F3′5′H is responsible for the anthocyanin biosynthesis branch in potato tubers. To further analyse the regulatory mechanism of F3′5′H, the transcriptome analysis identified 63 differentially expressed genes, which highly correlated with F3'5'H. Furthermore, correlations among the key differential metabolites and the differentially expressed genes indicated that 11 differential genes and 10 differential metabolites presented 76 significant correlations. These 11 genes mainly encoded serine/threonine protein kinase, UMP-CMP kinase, MADS-box transcription factor, and WD repeat-containing protein. The 10 differential metabolites were involved in pelargonidin, luteolin, kaempferol-3-O-rutinoside, eriodictyol-7-O-glucoside, and uridine monophosphate. Through yeast one-hybrid experiments, the proteins interacting with the promoter of F3'5'H were screened: ethylene-responsive transcription factor ERF011, gibberellin-regulated protein 9-like, and serine-threonine protein kinase, transcription factor LHW bHLH. These results will provide valuable insights into the regulation mechanism of the anthocyanin biosynthesis branch in potatoes.