Phenolic acids (rosmarinic acid, salvianolic acid B, etc.) in Salvia miltiorrhiza Bunge possess significant pharmacological activity and thus have high medicinal and economic value. Tyrosine aminotransferase (TAT, EC 2.6.1.5) is one of the key enzymes in the phenolic acid metabolic pathway, and the biological function and regulatory mechanism of its family member SmTAT2 have not been reported in S. miltiorrhiza. Through a transgenic assay (Overexpression and CRISPR/Cas9), we demonstrated that SmTAT2 can positively regulate the accumulation of phenolic acid. By using molecular interaction (Yeast single hybrid, Dual-LUC and EMSA) and transgenic technologies, we demonstrated that SmNAC36 first activates the transcription of SmMYB18, and SmMYB18 subsequently activates the expression of the target gene SmTAT2 to promote phenolic acid biosynthesis. Moreover, SmNAC36 can directly activate the transcription of SmTAT2. The molecular mechanism underlying the induced synthesis and accumulation of phenolic acid in Salvia miltiorrhiza by NAC36-MYB18-TAT2 molecular model is revealed. These results provide novel insights into the metabolic pathways of phenolic acids and a theoretical basis for their metabolic engineering and synthetic biology research.